Radiation therapy patient platform

ABSTRACT

Described here are systems, devices, and methods for imaging and radiotherapy procedures. Generally, a radiotherapy system may include a radiotransparent patient platform, a radiation source coupled to a multi-leaf collimator, and a detector facing the collimator. The radiation source may be configured to emit a first beam through the collimator to provide treatment to a patient on the patient platform. A controller may be configured to control the radiotherapy system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/814,276, filed on Nov. 15, 2017, now issued U.S. Pat. No. 10,702,715,and titled “RADIATION THERAPY PATIENT PLATFORM,” which claims priorityto U.S. Provisional Application Ser. No. 62/422,494, filed on Nov. 15,2016, and titled “RADIATION THERAPY PATIENT PLATFORM,” the content ofeach of which is hereby incorporated by reference in its entirety.

FIELD

The current invention relates to systems, devices, and methods forcontrol of radiation therapy. The systems, devices, and methods may beused for emission-guided high-energy photon delivery.

BACKGROUND

Radiation therapy, or radiotherapy, uses high-energy photons to treat avariety of diseases. For instance, radiotherapy is commonly applied tocancerous tumors. Some radiotherapy systems deliver a beam of photons toa tumor using a radiation source or linear accelerator (linac) system. Alinac may be mounted on a gantry that rotates around a patient. Thegantry may be a C-arm gantry or a circular gantry. The linac may berotated about the patient to concentrate a dose of photons at the tumorand reduce the radiation exposure of healthy tissue surrounding thetumor. A patient may be placed on a patient couch that moves in and outof a bore of a circular gantry for a patient to receive treatment.

For a rotating radiotherapy system to deliver effective treatment, thepatient couch, herein referred to as a patient platform, must be nearlyradiotransparent in a treatment beam plane and provide rigid support toa patient as the patient platform is cantilevered into and out of thebore of the gantry. However, due to a patient's weight and the length ofplatform, the platform will typically sag and introduce errors into abeam treatment plan. Moreover, typical carbon fiber patient platformsprovide a generally uncomfortable, flat or slightly curved surface for apatient to lie on. This is of little consequence for imaging proceduresthat may be completed fairly quickly (e.g., in under an hour). Bycontrast, some radiotherapy treatments may require a patient to remainstill for much longer periods of time (e.g., over an hour). Therefore,additional systems, devices, and methods for patient platform controland radiotherapy procedures may be desirable.

BRIEF SUMMARY

Described here are systems, devices, and methods for controlling theposition of a patient in a radiotherapy system. Also described hereinare systems, devices and methods for measuring patient platform sagduring a treatment session, which may be used to aid delivery ofradiotherapy treatment. In some variations, a system may comprise apatient platform having a patient region and a longitudinal axis, and aradiopaque elongate element coupled to the patient platform. Theelongate element may comprise a longitudinal axis parallel to thelongitudinal axis of the platform. Methods of quantifying a change inlocation of a radiotherapy patient platform due to a patient's weightmay comprise emitting a first beam from a radiation source through amulti-leaf collimator to irradiate the radiopaque element. Themulti-leaf collimator leaf pattern may be configured such that the firstbeam irradiates the radiopaque elongate element with little (if any)irradiation of the patient region of the patient platform. The firstbeam may be received by a detector facing the radiation source. A firstlocation of the elongate element (e.g., when the platform is unweightedin the absence of a patient) may be determined using the detector. Aftera patient lies on the patient platform, a second beam may be emittedfrom the radiation source through the multi-leaf collimator, themulti-leaf collimator having the same leaf pattern as when the firstbeam was emitted. A second location of the elongate element (e.g., whenthe platform is weighted in the presence of a patient) may be determinedusing the detector. A change in location of the elongate element may becalculated between the first location and a second location of theelongate element, where the second location may correspond to a weightedplatform. The change in location of the platform may be determined usingthe change in location of the elongate element.

The radiotransparent patient platform may comprise a first materialsubstantially transparent to high energy photons and the radiopaqueelement may comprise a second material substantially opaque to the highenergy photons. In some variations, the first location of the elongateelement may be determined from a plurality of images of the elongateelement using a radiation beam detector. In other variations, the firstbeam may be emitted from the radiation source relative to a horizontalplane between a first positive rotation angle and a second negativerotation angle. In some of these variations, the first beam may beemitted from the radiation source with the radiation source parallel tothe horizontal plane.

In some variations, a radiotransparent patient platform system maycomprise a radiotransparent patient platform having a radiopaqueelongate element located along a longitudinal axis parallel to alongitudinal axis of the platform. The radiotransparent patient platformmay comprise a first material substantially transparent to high energyphotons and the radiopaque elongate element may comprise a secondmaterial substantially opaque to the high energy photons. The patientplatform may comprise a first side having a patient support and a secondside opposite the first side. The elongate element may be coupled to thesecond side of the patient platform. A radiotransparent support elementmay couple the elongate element to the patient platform. In somevariations, the elongate element may comprise a metal rod. A radiationsource may be coupled to a multi-leaf collimator. The radiation sourcemay be configured to emit a first beam through the collimator toirradiate the elongate element. A detector may face the collimator andbe configured to receive the first beam. A controller may be configuredto determine a first location of the elongate element using the detector(e.g., when the platform is unweighted), calculate a change in locationof the elongate element between the first location and a second locationof the elongate element, where the second location corresponds to aweighted platform, and determine the change in location of the platformusing the change in location of the elongate element.

Also described herein are methods for quantifying a change in locationof a radiotherapy patient platform due to a patient. A patient platformmay optionally comprise one or more optical markers, and a method ofquantifying changes in the location of the platform may comprise imagingthe one or more optical markers using an optical sensor. The one or moreoptical markers may comprise a longitudinal axis parallel to alongitudinal axis of the platform. The optical sensor may be coupled toa rotatable gantry. A first location of the optical marker may bedetermined using the optical sensor. A change in location of the opticalmarker may be calculated between the first location and a secondlocation of the optical marker. The second location may correspond to aweighted platform. The change in location of the platform may bedetermined using the change in location of the one or more opticalmarker. In one variation, the second location of the optical marker maybe determined using a plurality of images of the one or more opticalmarkers (e.g., acquired by the optical sensor as the gantry rotatesaround the patient platform). A controller may be configured todetermine a first location of the one or more optical markers using theone or more optical sensors (when the platform is unweighted). Thesecond location may correspond to a weighted platform.

In some variations, the optical sensor may comprise an infrared sensorand/or an infrared illumination source. In another variation, theoptical marker may comprise a retroreflector or reflector. In yetanother variation, the optical sensor may comprise a laser. In onevariation, the patient platform may comprise a first side including apatient support and a second side opposite the first side. The opticalmarker may be coupled to the second side of the patient platform.

Also described here are systems, devices, and methods for qualityassurance of radiotherapy systems. For example, in order to determinewhether a desired dose of radiation is being delivered by a radiotherapysystem, radiation may be applied to a phantom comprising radiationsensors (e.g., dosimeter) at various locations in the phantom. Thephantoms described herein may aid in calibration of the variouscomponents of a radiation system (e.g., radiation source, radiationdetector, etc.). Generally, a system may comprise a patient platformhaving a patient support surface and an underside surface opposite thepatient support surface. A phantom may be mounted to the undersidesurface. The phantom may comprise a plurality of steps having acorresponding predetermined depth, and a plurality of radiationdetectors. Each of the radiation detectors may be disposed at thepredetermined depth of its corresponding step. Alternatively oradditionally, a phantom may comprise a plurality of radiation detectors,and a first region having a first density and a second region having asecond density different from the first density. The radiation detectorsand regions may each be arranged along the longitudinal axis.

In some variations, the radiation detectors may comprise ionizationchambers and dosimeter slots. Ionization chambers may be arranged alonga longitudinal axis of the phantom and along a vertical axisperpendicular to the longitudinal axis. The dosimeter slots may beparallel to the longitudinal axis and disposed at the predetermineddepth of its corresponding step. In some variations, at least one of thedosimeter slots may be nearly parallel to a vertical axis perpendicularto a longitudinal axis of the phantom. In some other variations, thephantom may comprise a housing that defines an internal fluid-tightvolume. A mount may couple the phantom to the patient platform. In someof these variations, the mount may be configured to slidably positionthe phantom relative to the patient platform.

In some variations, the radiation detectors may comprise ionizationchambers and dosimeter slots. In some of these variations, each of thedosimeter slots may intersect its corresponding ionization chamber. Theionization chambers and dosimeter slots may be spaced apart from eachother along the longitudinal axis. In some variations, a mount maycouple the phantom to the patient platform. The mount may be configuredto slidably position the phantom relative to the patient platform.

Also described are phantoms that may be useful for determining contrastresolution of a detector. In some variations, a system may comprise apatient platform having a patient support surface and an undersidesurface opposite the patient support surface, and a longitudinal axis. Aphantom may be mounted to the underside surface. The phantom maycomprise a first repeated pattern having a spatial frequency range and asecond repeated pattern having a contrast range. The first pattern maycomprise a series of high-contrast edges or stripes where the spacebetween the edges or stripes varies in accordance with the spatialfrequency range. The second pattern may comprise a series of repeatingshapes that have different levels of contrast with respect to abackground intensity. The first and second repeated patterns may bespaced along a longitudinal axis of the phantom. The spatial frequencyrange may be within a spatial frequency limit of a radiation detectorand the contrast range may be within a contrast limit of the radiationdetector.

In some variations, the first and second repeated patterns may comprisea set of contrasting shapes spaced apart at different intervals. The setof shapes may comprise a first shape having a first thickness and asecond shape having a second thickness different from the firstthickness. The set of shapes may comprise a first shape having a firstdensity and a second shape having a second density different from thefirst density. In some variations, a width of the phantom may be alignedparallel to a length of the patient platform. In some variations, thephantom may be disposed within an imaging region of the patientplatform. A mount may couple the phantom to the patient platform.

Also described herein are methods for adjusting a radiotransparentpatient platform to a patient's body contour, which may improve patientcomfort and radiotherapy procedure compliance. One variation of aradiotherapy patient platform systems may comprise a radiotransparentpatient platform having a conformable substrate having a plurality ofenclosures and a pressure sensor coupled to the conformable substrate. Acontroller may be configured to independently control a height of eachof the plurality of enclosures using the pressure sensor. A method foradjusting the contours of a conformable substrate may comprise measuringa pressure of the patient platform using the pressure sensor(s). Thepressure may comprise a plurality of enclosure pressures. The height ofeach of the plurality of enclosures may be independently controlledusing the pressure such that the conformable substrate contours to ashape of a patient. For example, the plurality of enclosures may becoupled to a pressure source.

In some variations, the method may further comprise determining apatient configuration corresponding to the height of each of theplurality of enclosures. The patient configuration may comprise at leastone of a pressure and the height of each of the plurality of enclosures.In some of these variations, the method may further comprise storing thepatient configuration in memory, and readjusting the height of each ofthe plurality of enclosures using the stored patient configuration. Inyet another variation, a thermoelectric layer of the patient platformmay be heated to form a compliant configuration, and cooling thethermoelectric layer may form a rigid configuration.

In some variations, a pressure channel may couple a pressure source toeach of the plurality of enclosures. In some of these variations, thepressure channel may comprise a radiotransparent material substantiallytransparent to high energy photons. In other variations, the pluralityof enclosures may comprise a fluid. In some of these other variations,the fluid may comprise a gas. In one variation, a thermoelectric layerand a heating element may each be coupled to the patient platform. Insome of these variations, the thermoelectric layer may transitionbetween a compliant configuration and a rigid configuration based ontemperature. In another variation, a thermal insulating layer may becoupled to the thermoelectric layer. In yet another variation, theplurality of enclosures may comprise a flexible membrane. In yet furthervariations, the plurality of enclosures may each comprise a honeycombconfiguration.

Also described here are methods for calculating sag of aradiotransparent patient platform. A weighted patient platform having areduced amount of sag may allow more accurate treatment planning andimproved delivery of radiotherapy treatment. The patient platform maycomprise an upper portion and a lower portion coupled to the upperportion. The upper portion and the lower portion may move relative torelative to each other or may move relative to a base. One variation ofa method may comprise emitting an imaging beam using an imagingradiation source in an imaging plane perpendicular to a longitudinalaxis of the patient platform. The lower portion may be non-intersectingwith the imaging plane and the upper portion may intersect the imagingplane.

In some variations, a treatment beam may be emitted from a treatmentradiation source coupled to a multi-leaf collimator in a treatment planeperpendicular to a longitudinal axis of the patient platform. The upperportion and the lower portion may be moved such that the lower portionis non-intersecting with the treatment plane and the upper portionintersects the treatment plane.

In other variations, moving the upper portion into the imaging plane maycomprise positioning the lower portion such that a leading edge of thelower portion is located at a first distance away from the imagingplane. In some of these other variations, moving the upper portion intothe treatment plane may comprise positioning the lower portion such thatthe leading edge of the lower portion is located at a second distanceaway from the treatment plane. The upper portion may comprise a firstmaterial substantially transparent to high energy photons and the lowerportion may comprise a second material substantially opaque to the highenergy photons.

One variation of a patient platform system may be configured tocoordinate movement of a patient platform with the timing of imagingand/or treatment beam emission. In general, these systems may comprise aradiotransparent patient platform having an upper portion coupled to alower portion. A base may be coupled to the lower portion of the patientplatform. A radiation source may be coupled to a multi-leaf collimator.A controller may be configured to move the upper portion relative to thelower portion such that the upper portion is within a beam plane of theimaging and/or treatment beam while the lower portion is not within thebeam plane (e.g., the lower portion may be non-intersecting with thebeam plane and the upper portion may intersect the beam plane). Theradiation source may be configured to emit a first beam in a beam planeperpendicular to a longitudinal axis of the patient platform.

Also described here are methods for controlling a radiotransparentpatient platform. The patient platform may comprise an upper portion anda lower portion fixed to the upper portion. The upper portion and thelower portion may comprise different radiotransparency. The patientplatform may move relative to a base. An imaging beam may be emitted byan imaging radiation source in an imaging plane perpendicular to alongitudinal axis of the patient platform. The lower portion may benon-intersecting with the imaging plane and the upper portion mayintersect the imaging plane.

In some variations, the methods may further comprise emitting atreatment beam from a treatment radiation source coupled to a multi-leafcollimator in a treatment plane perpendicular to a longitudinal axis ofthe patient platform. The patient platform may move such that the lowerportion is non-intersecting with the treatment plane and the upperportion intersects the treatment plane.

In other variations, moving the upper portion into the imaging plane maycomprise positioning the lower portion such that a leading edge of thelower portion is located at a first distance away from the imagingplane.

In some of these variations, the upper portion may move into thetreatment plane and may comprise positioning the lower portion such thatthe leading edge of the lower portion is located at a second distanceaway from the treatment plane. In another variation, the upper portionmay comprise a first material substantially transparent to high energyphotons and the lower portion may comprise a second materialsubstantially opaque to the high energy photons.

Also described herein are radiotherapy patient platform systems. Ingeneral, the systems described herein may comprise a radiotransparentpatient platform having an upper portion fixed to a lower portion. Abase may be coupled to the lower portion of the patient platform. Aradiation source may be coupled to a multi-leaf collimator. Theradiation source may be configured to emit a first beam in a beam planeperpendicular to a longitudinal axis of the patient platform. Acontroller may be configured to move the patient platform relative tothe base. The lower portion may be non-intersecting with the beam planeand the upper portion may intersect the beam plane.

Also described here are methods of irradiating a first region ofinterest of a patient. For example, a radiotherapy patient platform maybe moved with respect to one or more regions of interest to aid deliveryof radiotherapy treatment. In general, the methods may comprise moving aradiotherapy patient platform into a patient region of a gantry. Thegantry may define an isocenter point about which the gantry rotates. Anisocenter axis intersects the isocenter point and is in parallel with afirst longitudinal axis of the patient region. The patient platform maymove to position the first region of interest on the isocenter axis. Aradiation beam may be emitted to the first region of interest on theisocenter axis from a radiation source.

In some variations, moving the patient platform to position the firstregion of interest on the isocenter axis may comprise moving the patientplatform in a lateral direction. In other variations, at least one ofpitch and yaw of the patient platform may rotate. In some of thesevariations, a second longitudinal axis of the first region of interestmay align on the isocenter axis. In another variation, the patient maycomprise a second region of interest. The patient platform may move toalternately position the first and second regions of interest on theisocenter axis. In some of these variations, a third longitudinal axisof the second region of interest may be aligned with the isocenter axis.

Also described herein are radiotherapy patient platform systems. Forexample, a radiotherapy patient platform may comprise one or more drivesystems that may be configured to adjust the platform position orlocation with a plurality of degrees of freedom. In general, the systemsmay comprise a radiotransparent patient platform coupled to a base. Thepatient platform may comprise an upper portion coupled to a lowerportion. An axial drive system may be coupled to the patient platform.The axial drive system may be configured to move the patient platform inan axial direction relative to the base. A lateral drive system may becoupled to the patient platform. The lateral drive system may beconfigured to move the patient platform in a lateral direction relativeto the base. A vertical drive system may be coupled to the patientplatform. The vertical drive system may be configured to move thepatient platform in a vertical direction relative to the base. Thevertical drive system may comprise a first and second scissor elementcoupled to the patient platform. A pitch drive system may be coupled tothe platform. The pitch drive system may be configured to pitch theupper portion relative to the lower portion about a pitch pivot. A yawpivot may couple the upper portion to the lower portion at respectivefirst ends of the upper and lower portions. A yaw drive may be coupledto the first end of the upper portion. The yaw drive may be configuredto yaw the upper portion relative to the lower portion about the yawpivot.

In some variations, the pitch drive system may comprise a first wedgecoupled to the yaw drive system and a second wedge coupled to the upperportion. In some variations, the axial drive system may be coupledbetween the lower portion and the lateral drive system. The lateraldrive system may be coupled between the axial drive system and the yawdrive system. The yaw drive system may be coupled between the lateraldrive system and the pitch drive system. The pitch drive system may becoupled between the yaw drive system and the upper portion.

In some variations, the axial drive system may comprise an axial driveelement coupled to the first end of the lower portion and an axial railcoupled to the axial drive element. In other variations, the lateraldrive system may comprise a lateral drive element coupled to the patientplatform and a lateral rail coupled to the lateral drive element.

In another variation, the first scissor element may be coupled to thefirst end of the lower portion and the second scissor element may becoupled to a second end of the lower portion. In some variations, thevertical drive system may comprise a vertical drive element comprising afirst linear screw coupled to the first scissor element. In someinstances, the vertical drive element may comprise a second linear screwcoupled to the second scissor element.

In some variations, the radiotherapy patient platform systems describedherein may further comprise a handheld controller. The handheldcontroller may comprise a first switch and a docking port. The firstswitch may be configured to generate a movement signal. In somevariations, the first switch may comprise at least one of a button, ananalog stick, a trackball, a touch screen, a directional pad, a jogdial, a motion detector, an image sensor, and a microphone. In othervariations, the system may comprise a proximity sensor configured todetect a proximity of the controller to the patient platform. Thepatient platform may be configured to move using the movement signal andthe detected proximity. In another variation, the controller maycomprise a wireless transmitter outputting the movement signal. In yetanother variation, a tether may be coupled to the patient platform andthe controller. In further variations, the movement signal may controlat least four degrees of freedom of motion.

In some variations, the system may comprise a second switch. In some ofthese variations, the second switch may be a step switch. The controllermay be configured to output the movement signal upon activation of thefirst and second switches. The controller may comprise the second switchand a housing. The first switch may be provided on a first side of thehousing and the second switch may be provided on a second side of thehousing opposite the first side.

Some of the radiotherapy patient platform systems described here mayfurther comprise a head fixation device configured to hold a patienthead in a predetermined position relative to a patient platform.Generally, the head fixation device may comprise having a hinge coupledto a base, a head rest coupled to the hinge, and a drive system coupledto the head rest. The drive system may be configured to extendsubstantially perpendicularly to the base. The head rest and the drivesystem may each comprise a radiotransparent material substantiallytransparent to high energy photons.

In some variations, the drive system may comprise a pneumatic element.In other variations, the drive system may comprise an electromechanicalelement. In another variation, an actuator may be coupled to the drivesystem. The actuator may be coupled to a first end of the patientplatform. In further variations, the hinge may comprise a lock having aplurality of detents and a pin.

Also described here are methods of positioning a patient's head relativeto a radiotherapy patient platform. For example, a head fixation devicemay be used to position a patient's head with respect to a patientplatform to aid delivery of radiotherapy treatment. In general, themethods comprise coupling a patient's head to a head fixation devicecomprising a base coupled to a head rest by a hinge and a head restdrive system coupled to the head rest. The drive system may be extendedsubstantially perpendicularly to the base.

In some variations, the head rest may be locked relative to the base. Inother variations, at least one of a patient torso and a patient shouldermay be coupled to the base. In some other variations, the head rest maybe pitched and yawed relative to the base. In yet other variations, thehead rest may be pivoted about the hinge in response to neck flexion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1F are illustrative depictions of variations of a radiotherapypatient platform system. FIG. 1A is a cross-sectional side view of avariation of a patient platform and gantry. FIGS. 1B-1F arecross-sectional front views of variations of the patient platform andgantry of FIG. 1A.

FIGS. 2A-2C are illustrative depictions of variations of a radiotherapypatient platform. FIG. 2A is a perspective view of a variation of apatient supported by a conformable patient platform. FIG. 2B is aperspective view of the conformable patient platform of FIG. 2A. FIG. 2Cis a cross-sectional side view of another variation of a patientsupported by a conformable patient platform.

FIGS. 3A-3D are illustrative depictions of variations of a radiotherapypatient platform system. FIGS. 3A-3B are cross-sectional side views of avariation of a telescoping patient platform and gantry. FIGS. 3C-3D arecross-sectional side views of another variation of a telescoping patientplatform and gantry.

FIGS. 4A-4F are illustrative depictions of variations of a radiotherapypatient platform system. FIGS. 4A-4B are side views of a variation of apatient platform system. FIG. 4C is a perspective view of the patientplatform system of FIG. 4B. FIG. 4D is a side view of another variationof a patient platform system. FIG. 4E is a perspective view of thepatient platform system of FIG. 4D. FIG. 4F is a perspective view of thepatient platform system of FIG. 4C.

FIG. 5 is an illustrative cross-sectional side view of a variation of ahandheld controller for a radiotherapy system.

FIGS. 6A-6B are illustrative side views of a variation of a headfixation device.

FIG. 7 is a flowchart representation of one variation of a radiotherapyprocess.

FIG. 8 is a flowchart representation of one variation of a patientplatform sag determination process.

FIG. 9 is a flowchart representation of one variation of an elongateelement location determination process.

FIG. 10 is a flowchart representation of one variation of a patientplatform loading process.

FIGS. 11A-11B are flowchart representations of variations of a patientplatform loading process.

FIG. 12 is a flowchart representation of another variation of a patientplatform moving process.

FIGS. 13A-13E are illustrative plan views of variations of aradiotherapy patient platform.

FIG. 14 is a flowchart representation of one variation of a patient headfixing process.

FIG. 15 is an illustrative depiction of sag of a patient platform.

FIGS. 16A and 16B are illustrative cross-sectional side views of avariation of a phantom for a radiotherapy system.

FIG. 17 is an illustrative cross-sectional side view of a variation of aphantom for a radiotherapy system.

FIG. 18 is an illustrative plan view of a variation of a phantom for aradiotherapy system.

DETAILED DESCRIPTION

Described herein are systems, devices, and methods useful forradiotherapy procedures. As used herein, radiotransparent refers to theproperty of being substantially transparent to high energy photons inthat there is little or no attenuation of high energy photons.Conversely, radiopaque refers to the property of being substantiallyopaque to high energy photons. For instance, a radiopaque material mayattenuate or block transmission of high energy photons.

Generally, to perform an imaging and/or radiotherapy procedure, apatient is loaded onto a patient platform. The patient platform maycomprise carbon fiber due to its radiotransparency and ability toprovide rigid support to a patient. Once loaded, the platform is movedinto a patient region (e.g., bore, central opening, cavity) of a ringgantry. Typically, the large size and geometry of the gantry setsphysical constraints on the configuration of the patient platform andother system components. In some radiotherapy systems, a gantry maycomprise a C-arm shape that defines a patient region through which thepatient platform may be extended into and out of. The gantry maycomprise one or more beam delivery systems that may rotate about thepatient platform and provide one or more imaging and/or treatment beamsfrom a plurality of angles. In order to precisely and/or accuratelydeliver a treatment beam to a region of interest (e.g., lesion, tumor)of the patient, the location of the patient with respect to the gantrymust be accurately determined and account for any sag, deviation, ordeflection of the patient platform in the treatment beam plane. Itshould be appreciated that effective radiotherapy treatment is not onlythe ability to deliver high energy photons to a region of interest totreat a disease, but to do so while reducing delivery of high energyphotons to healthy tissue. Otherwise, for example, a cancerous tumor maybe treated at the cost of damage to healthy organs and tissue.

Described further herein are systems, devices, and methods ofcontrolling movement of a patient platform. For ease of explanation, aset of reference axes are defined in FIG. 15 to define a set of axes oftranslation and rotation with respect to a patient platform (1500), andare used throughout (e.g., FIGS. 1A-1F, 3A-3D, 4A-4F, 6A-6B, 13A-13E,16A-16B, 17, 18 , etc.) In particular, FIG. 15 is an illustrativedepiction of sag (1520) of a patient platform (1500) in an X-Y plane.The patient platform (1500) may be coupled to and extend from a base(1502). A sag (1520) of the patient platform (1500) corresponds to thevertical distance (along the Z-axis) between a horizontal plane (1510)(e.g., X-Y plane) and the sagging patient platform (1500). Thehorizontal plane (1510) corresponds to the plane of an idealized patientplatform mounted on the base (1502) that extends from the base (1502)without any deflection. As shown in FIG. 15 , the sag (1520) of thepatient platform (1500) may increase along the length of the patientplatform (1500) extending from the base (1502). As used herein, axialmovement corresponds to movement along the X-axis, vertical movementcorresponds to movement along the Z-axis, and lateral movementcorresponds to movement along the Y-axis (which extends into and out ofthe X-Z plane). As illustrated in FIG. 15 , yaw rotation corresponds torotation about the Z-axis and pitch rotation corresponds to rotationabout the Y-axis.

In some variations of the system, a sag of an ideal patient platform maybe measured and used to aid delivery of radiotherapy treatment. Forinstance, measuring the degree to which a patient platform sags may beused to adjust a treatment plan in order to accurately and/or moreprecisely apply radiation to a region of interest of a patient. In someof these variations, a patient platform may comprise a radiopaqueelongate element. One or more leaves of a multi-leaf collimator of thegantry may be opened to selectively direct an imaging beam to intersectthe elongate element and a detector located across from a radiationsource as the gantry rotates about the patient platform. Various methodsmay be used to determine an amount of sag of the elongate element usingthe detector data, for example, a Winston-Lutz based method. Inaccordance with systems, devices, and methods herein, the patientplatform sag and the location of the region of interest may bedetermined. Furthermore, by selecting image beam angles where radiationbeams intersect the elongate element and not the patient, a location ofa region of interest may be determined without exposing the patient toadditional radiation. Accordingly, a treatment dose may be moreaccurately and/or more precisely delivered to a patient, thus sparinghealthy tissue and improving dose delivery.

In some variations of the system, a conformable patient platform may beprovided to improve patient platform ergonomics, reduce patientregistration and setup time, and increase patient compliance. In somecases, a patient may be sedated to limit their movement on a patientplatform. However, sedation poses risks and may be undesirable for somepatient groups such as the elderly, patients with advanced disease,and/or patients taking medication. A conformable patient platform mayfacilitate patient comfort and encourage the patient to remainmotionless for longer periods of time to receive radiotherapy treatmentand may help to reduce the use of sedatives. In some of thesevariations, a configuration of the patient platform that may be uniqueor customized for a particular patient may be saved in a memory of thecontroller and may be reapplied for future procedures. The patientplatforms described in further detail below may uniquely conform to eachpatient and serve as an ergonomic restraint to limit patient movement onthe patient platform. Importantly, the conformable patient platform maybe radiotransparent and it should be appreciated that the patientplatforms described herein may be used for diagnostic imaging and/orradiotherapy procedures. In some variations, the patient platform maycomprise a conformable substrate having a plurality of independentlyheight adjustable enclosures that may deform and rigidize to contour toa shape of a patient. In other variations, the patient platform maycomprise a thermoelectric layer that forms a compliant configurationwhen heated and a rigid configuration when cooled.

Some variations of the patient platform, as described in further detailbelow, may telescope (e.g., portions of the platform may move relativeto each other, where one portion of the platform may extend from anotherportion to make the entire platform longer) to reduce a sag of a patientplatform. For example, some patient platforms may be formed of a singlepiece of carbon fiber cantilevered so as to extend from a base. Whilethese platforms are radiotransparent, they may progressively sag as theyextend out from a mounting base and into a patient region of a gantry.As shown in FIG. 1A, for example, a first end (105) of the patientplatform (102) will exhibit less sag than a second end (107). Inaccordance with some of the variations of the invention, a patientplatform may comprise a plurality of portions that may move or telescoperelative to each other and/or a base of the patient platform. A firstportion of the patient platform may be formed of a radiotransparentmaterial while a second portion may be formed of a stiffer material (ofany radiotransparency) that exhibits less sag than the first portion.The patient platform may be controlled such that the stiffer secondportion is cantilevered from a base and moves right up to, but does notcross the plane of an imaging beam and/or treatment beam that wouldotherwise interfere with an imaging and/or treatment procedure.Accordingly, the patient platform as a whole may exhibit greaterrigidity to reduce sag of the patient platform.

In some variations of the system, as described in further detail below,a patient platform may move with a plurality of degrees of freedom toposition a patient and aid delivery of radiotherapy treatment. Someconventional patient platforms provide a motor at each axial end of apatient platform to provide yaw control. These conventional motors mayutilize radiopaque wires that extend along a length of the patientplatform through a treatment beam plane and undesirably interfere withimaging and/or treatment. By contrast, in some variations of the presentinvention, a patient platform may comprise a yaw drive and axial drivesystem coupled to a first end of a patient platform and be configured toyaw about a pivot point without decreasing radiotransparency of thepatient platform. In other variations, the patient platform may comprisea vertical drive system configured to control a height and/or pitch ofthe patient platform that may, for example, be useful for treatment ofcranial lesions. In some variations of the methods for deliveringradiotherapy treatment, a patient platform may position a region ofinterest on an isocenter of a gantry such as an isocenter of a beamsource to focus radiation dose to the region of interest and reduceradiation dose to healthy tissue.

Described further herein are systems, devices, and method forcharacterization, qualification, verification, and/or calibration ofradiotherapy systems. In order to assess or confirm that the componentsof the radiotherapy system are configured to deliver a desired radiationdose precisely and accurately to target regions in a patient, the systemmay undergo quality assurance testing, registration, calibration, and/orverification procedures prior to a treatment session and/or atpredetermined intervals (e.g., daily, monthly, quarterly, etc.). Suchprocedures may comprise measuring the emission or radiation using one ormore radiation detectors positioned at predetermined locations. Forexample, a phantom having a plurality of radiation detectors may bedisposed on or below a patient platform. A phantom may comprise aplurality of dosimetry sensors and types configured to receive a dose ofradiation. Dose data generated from the phantom may be compared to a setof reference dose data to determine calibration of one or morecomponents (e.g., detector) of the radiotherapy system.

Some variations of the patient platform systems may comprise a handheldcontroller for controlling a patient platform. Radiotherapy systemoperators may adjust the position of a patient with respect to a gantryby controlling movement of the patient platform using the handheldcontroller. For example, one or more switches may be integrated into ahousing of the controller for a user to operate. The controller may bedocked to a gantry or patient platform to enable a first set of controlfunctionality and undocked from the system to enable a second set ofcontrol functionality. The handheld controller, as described in furtherdetail below, may generate a movement signal. Furthermore, control ofthe patient platform may be limited to a predetermined proximity of thesystem. Thus, the operator may gain increased mobility while ensuringpatient safety and compliance with regulations.

It is generally desirable for a radiotherapy procedure to deliver atreatment beam from a plurality of angles, which may help to reduceradiation dose to healthy tissue. This may be especially desirable forthe head and neck as the salivary glands, eyes, ears, and nerve cellsmay be particularly sensitive to radiation dose. In some variations, ahead fixation device may be useful to precisely position a patient'shead on a patient platform. However, some patients experience difficultyand/or discomfort with devices that attach to the head and/or controlhead movement. The head fixation devices, as described in further detailbelow, may allow a patient to manually move their head through neckflexion to a desired position and lock or secure their head in place fortreatment. Additionally or alternatively, a patient and/or operator maycontrol a drive system such as a pneumatic drive system to repositionand lock or secure the head in a desired position. Any of the systems,devices, and methods described below may be used in combination. Thevariations as described here below may improve patient comfortassociated with radiotherapy procedures.

I. Systems

Radiotherapy Patient Platform

Generally, the systems described here may be useful in determining a sagof a patient platform and a location of a region of interest of apatient on the patient platform. FIG. 1A is a cross-sectional side viewof a radiotherapy patient platform system (100). The system (100) maycomprise a patient platform (102), a gantry (120), and base (112). Thepatient platform (102) may comprise a radiotransparent first material,such as carbon fiber. The patient platform (102) may further comprise afirst side (104) (top surface) comprising a patient support on which apatient (114) may lay on. A second side (106) (underside) of the patientplatform (102) may be provided opposite the first side (104). In somevariations, the patient platform (102) may have a length of about1.5-3.0 meters, a width of about 0.50-2.0 meters, and a thickness ofabout 0.05-0.50 meters, and may preferably have a length of 2 meters, awidth of 0.50 meter, and thickness of 0.10 meters. As shown in FIG. 1A,at least a portion of the patient platform (102) may be extended from anedge of a base (112) (e.g., cantilevered) such that a second end (107)of the patient platform (102) may progressively sag due to the weight ofthe patient (114). In some variations, a radiopaque elongate element(108) may be coupled to the second side (106) of the patient platform(102). The elongate element (108) may be fixed to the patient platform(102) such that an amount of space between the elongate element (108)and patient platform (102) is a constant or a known quantity (e.g., thepatient platform (102) and elongate element (108) may be separated bythe thickness of a support element (110)). In some instances, aradiotransparent support element (110) may couple the radiopaqueelongate element (108) to the patient platform (102). In somevariations, the elongate element (108) may have a thickness of about0.001-0.01 meters and the support element (110) may have a thickness ofabout 0.001-0.50 meters.

In some variations, the elongate element (108) may be formed of aradiopaque second material. By imaging the elongate element (108) fromone or more gantry angles using a first radiation beam (126), a locationof the elongate element (108) may be precisely determined. In someinstances, the elongate element (108) may comprise a metal such asaluminum, although other radiopaque materials and combinations ofradiopaque materials may be used. As shown in FIGS. 1A-1D and 1F, theelongate element (108) may comprise a wire or rod shape. In somevariations, a length of the elongate element (108) may correspond to alength of the region of interest (116) of the patient (114). In othervariations, the elongate element (108) may correspond to a length of thepatient platform (102) through which a first beamlet (127 a) mayintersect and pass through. It should be noted that any length of theelongate element (108) may be selected so long as the elongate element(108) is located at a position where sag determination is desired.Additionally or alternatively, the radiotransparent support element(110) may couple to one or more radiopaque spheres (e.g., bead, ball,pellet, orb, etc.) in any of the variations described herein.

A first end (105) of the patient platform (102) may be coupled to a base(112). The base (112) may be provided external to a patient region (140)of the gantry (120) and may not be radiotransparent. In the variationsdepicted in FIGS. 1B-1E, the gantry (120) may comprise a radiationsource (122) and a multi-leaf collimator (124) to generate and direct afirst beam (126) at the radiopaque elongate element (108) and detector(128) facing the multi-leaf collimator (124). A controller (130) maycomprise a processor and memory to determine the sag of the patientplatform (102) using the detector data, as described in further detailbelow. It should be appreciated that the first beam (126) directed atthe elongate element (108) may be generated by a radiation source (122)without the multi-leaf collimator (124).

FIG. 1B is a cross-sectional front view of a patient platform (102) andgantry (120) illustrating the intersection of a first beamlet (127 a)with the radiopaque elongate element (108) and detector (128). As shownin FIG. 1B, the elongate element (108) may be provided on a second side(106) of the patient platform (102) and coupled to the patient platform(102) by a radiotransparent support element (110). Radiation source(122) may be rotated around the patient region by the gantry (120) suchthat a first beamlet (127 a) and a second beamlet (127 b) may be emittedfrom above, below, and the sides of the patient (114). Although theradiation source (122) may rotate circularly around the patient gantry(120), FIGS. 1B-1C and 1E illustrate the radiation source (122) withinthe gantry (120) as it is aligned to a horizontal plane (118) (e.g., X-Yplane).

A predetermined estimate of patient platform sag may be used todetermine which leaves of the multi-leaf collimator (124) to open todirect the first beamlet (127 a) at the radiopaque elongate element(108) and detector (128). For example, estimates of patient platform sagfor a given patient weight may be stored in a database in memory andused to determine a set of leaves of the multi-leaf collimator (124) toopen for a given gantry angle. The controller (130) controlling theradiation source (118) and multi-leaf collimator (124) may ensure thatthe first beamlet (127 a) does not intersect the patient (114).Optionally, the multi-leaf collimator (124) may open one or more leavessuch that a second beamlet (127 b) irradiates region of interest (116).Emission of a radiation beam (126) from the radiation source (122) atthe gantry angle depicted in FIGS. 1B-1C and 1E may permit the radiationtherapy system to provide therapeutic radiation to the region ofinterest (116) using the second beamlet (127 b) while concurrently(e.g., simultaneously or sequentially) collecting image data for patientplatform (104) position information (e.g., sag data) using the firstbeamlet (127 a). In FIGS. 1B-1C, the beam (126) emitted from theradiation source (122) through the multi-leaf collimator (124) mayselect the first beamlet (127 a) to intersect the elongate element (108)without intersecting the patient (114). More generally, the firstbeamlet (127 a) may be emitted at the elongate element (108) from anygantry angle so long as the first beamlet (127 a) does not intersect thepatient (114). Consequently, determination of patient platform sag maynot increase radiation dose to the patient (114). In some variations,the first beamlet (127 a) may be emitted toward the radiation source(122) relative to the horizontal plane (118) between a first positiverotation angle (α₁) and a second negative rotation angle (α₁) of about±45°. The duration and power of the first beamlet (127 a) is notparticularly limited as the first beamlet (127 a) does not intersect thepatient (114). Irradiation of the elongate element (108) by the beamlet(127 a) may be detected by the detector (128), and this detector datamay be used to locate the elongate element (108) of the patient platform(102) weighted by the patient (114) relative to a known location of theelongate element (108) of an unweighted patient platform (102). Thedifference in these locations corresponds to an amount of sag of thepatient platform (102). Detector data generated from a plurality ofgantry angles may thus improve real-time sag determination.

It should be appreciated that one or more radiopaque elongate elements(108) may be coupled to the patient platform (102), so long as a firstbeamlet (127 a) that intersects the elongate element (108) does notintersect the patient (114). In some variations, two or more elongateelements (108) may be coupled to the patient platform (102) byrespective radiotransparent support elements (110) at a predetermineddistance (D) from each other. In some examples, the elongate elements(108) may comprise a pair of cylindrical rods of the same or differentdimensions (e.g., length, diameter) provided along different portions ofthe patient platform (102). In FIG. 1C, one of the elongate elements(108) is disposed on a first side (e.g., left side) of the patientplatform (102) while another elongate element (108) is disposed on asecond side (e.g., right side) of the patient platform (102). Theelongate elements (108) may be disposed in parallel to a longitudinalaxis of the patient platform (102). The elongate elements (108) depictedin FIGS. 1C-1D may have the same or different shape and/or dimension. Inother variations, three or more radiopaque elements (e.g., elongateelements (108) and/or radiopaque spheres) may be coupled non-collinearlyto the patient platform (102). That is, the radiopaque elements mayintersect the same line except for at least one of the radiopaqueelements. For example, a first and second radiopaque element may bedisposed along a line parallel to the Y-axis (e.g., width of the patientplatform (102)) while a third radiopaque element may be disposed betweenthe first and second radiopaque element along the Y-axis and spacedapart along the X-axis (e.g., length of the patient platform (102)) fromthe first and second radiopaque element). In one variation, the threeradiopaque elements may comprise any combination of shapes anddimensions as discussed above. For example, the radiopaque elements maycomprise three spheres (e.g., beads) or three elongate elements (e.g.,rods), two spheres and one rod, and one sphere. The shape, size,dimensions, and locations of the one or more radiopaque elements may bestored in a memory of a controller.

In another variation, as illustrated in FIG. 1D, each elongate element(108) may be imaged using corresponding beamlets (132, 134). Similar toFIG. 1C, the elongate elements (108) may be disposed on opposite sidesof the patient platform (102). The beamlets (132, 134) may be emittedfrom a beam assembly (123) including multi-leaf collimator and radiationsource. Imaging of the elongate elements (108) using different beamlets(132, 134) may increase the number of gantry angles from which theelongate elements (108) may be imaged since each beamlet need notintersect both elongate elements (108). In the variation depicted inFIG. 1D, patient platform sag measurements may be acquired withoutirradiating the patient. This may help to reduce the radiation exposureof the patient.

Both of the elongate elements (108) may be imaged using one or morebeamlets at a predetermined gantry angle. The detector data generated byone or more beamlets may be used to determine an amount of patientplatform (102) sag. As best illustrated in FIG. 1D, for one or morebeamlets (132, 134) emitted at a given gantry angle, the detector (128)will generate detector data having projections of the elongate elements(108) separated by a projection distance (D′). Sag of a patient platform(102) corresponds with the projection distance (D′) such that a changein the projection distance (D′) indicates a change in the sag of thepatient platform (102). For example, an increase in distance (D′) maycorrespond to an increase in sag of the patient platform (102). Thus,patient sag may be determined using one or more beamlets emitted from asingle gantry angle. Of course, the elongate elements (108) may beimaged from a plurality of gantry angles to generate detector data.

Additionally or alternatively, the elongate elements (108) may be imagedby beamlets from a plurality of gantry angles to determine an absolutelocation of the elongate elements (108). For example, a first elongateelement disposed on a first side (e.g., left side) of the patientplatform (102) may intersect a first beamlet emitted from a first sideof the gantry (120) (e.g., left side of FIG. 1C) from a set of anglesrelative to the horizontal plane (118). Similarly, a second elongateelement disposed on a second side (e.g., right side) of the patientplatform (102) may intersect a second beamlet emitted from a second sideof the gantry (120) (e.g., right side of FIG. 1C) from a set of anglesrelative to the horizontal plane (118). Thus, the pair of elongateelements may be imaged from left and right sides of the patient platform(102) to increase the number of angles from which the elongate elementsmay be imaged and thereby improve patient platform sag determination.

In addition to determination of sag, differences in the absolutelocations of the elongate elements (108) relative to each other may beused to calculate a roll of the patient platform (102), that is arotation of the patient platform (102) about a longitudinal axis of thepatient platform (102) (e.g., X-axis in FIG. 1C). For example, each ofthe elongate elements (108) in FIG. 1C may be coupled to the patientplatform (102) at equal heights from the second side (106) of thepatient platform (102). If the height of one of the elongate elements(108) changes relative to the other elongate element (108), then thepatient platform (102) has rolled (e.g., twisted) a correspondingamount. Thus, a change in location of the patient platform (102) due toa patient (114) disposed on the patient platform (102) may be determinedalong multiple axes.

In another variation, the patient platform (102) may comprise threenon-collinear elongate elements (108) used to calculate roll and yawusing the absolute locations of the three elongate elements (108)relative to each other. For example, the three elongate elements (108)may be coupled to the patient platform (102) spaced apart along theX-axis and Y-axis of the patient platform (102). If the detector dataprojections of the elongate elements (108) along the X-axis change indistance, then the patient platform (102) has yawed (e.g., turned) acorresponding amount. Thus, a sag, roll, and yaw of the patient platform(102) due to a patient (114) may be determined using a set of elongateelements (108) and at least two beamlets.

FIG. 1E is another cross-sectional front view of a patient platform(102) and gantry (120) illustrating the intersection of a first beamlet(127 a) with a radiopaque elongate element (109) that extends in awidthwise direction. This configuration may allow imaging from oppositesides of the gantry (120) (e.g., left and right sides of a patient(114)). As shown in FIG. 1E, the radiopaque elongate element (109) maycomprise a thin metallic foil (e.g., a metal sheet). A thin, wide foilhaving a width greater than thickness may provide significantattenuation only in the direction along the width of the foil (e.g.,along the plane of the metal sheet) such that the foil does notsignificantly attenuate imaging beams at other angles. In someinstances, the elongate element (109) may comprise aluminum and have athickness of about 0.0001-0.001 meters and a width of about 0.10-0.5meters.

In some variations, the elongate element (108, 109) may comprise aplurality of materials and configurations. For instance, the elongateelement (108, 109) may form a radiotransparent portion and one or moreradiopaque portions where the radiopaque portions may form identifiableshapes after image processing. In some instances, the imaged radiopaqueelongate element (108, 109) may display one or more symbols (e.g.,numbers, letters), geometric shapes, and other fiducials correspondingto predetermined locations along a length of the patient platform (102)that may aid patient platform sag determination.

In some variations, the patient platform (102) may comprise one or moreradiopaque portions without coupling to an elongate element (108, 109)and/or radiotransparent support element (110). For instance, aradiopaque portion may be coupled to an edge of the patient platform(102) by a fastener, adhesive, and the like.

Additionally or alternatively, the elongate element may not beradiopaque so long as an image contrast may be formed with the patientplatform. It should be appreciated that any material able to generate animage contrast with respect to the radiotransparent patient platform(102) may be used. In some variations, the patient platform (102) maycomprise a plurality of bores (e.g., elongate holes) for detecting sagof a patient platform (102). For example, a radiotransparent supportelement (110) may couple to a second side (106) of the patient platform(102) and comprise one or more bores that allow portions of a radiationbeam (126) to pass through unimpeded and be received by a detector(128). A bore may, for example, extend in a longitudinal direction(e.g., along the X-axis) as an elongate bore or have a spherical shape.In another example, the support element (110) may comprise aluminum toenhance an image contrast between the empty space within the bore andthe support element (110). It should be appreciated that the shape ofthe bore is not limited so long as the detector data of the bore may beused to determine a location of the patient platform (102). For example,a bore may comprise a rod shape or a spherical shape as discussed above.In some variations, a length of the bore may correspond to a length ofthe region of interest (116) of the patient (114). In other variations,the bore may correspond to a length of the patient platform (102)through which a first beamlet (127 a) may intersect and pass through.

The bore may comprise a plurality of shapes and sizes, as discussedabove. In some instances, the bore may have a diameter of about0.001-0.01 meters. Although the support element (110) and patientplatform (102) may be radiotransparent, a faint outline of the supportelement (110) and patient platform (102) may still be visible whenimaging the platform (102) such that an image contrast between a solidportion of the patient platform (102) and one or more bores within thesupport element (110) and/or patient platform (102) may serve as afiducial for location tracking. Detector data may be used to locate oneor more bores of the support element (110) and/or patient platform (102)relative to a known location. The difference in these locationscorresponds to an amount of sag of the patient platform (102). In thismanner, sag of the patient platform (102) may be determined without theartifacts associated with high density, radiopaque materials.

FIG. 1F is cross-sectional front view of a patient platform (102) andgantry (120) comprising an optical sensor (150) configured to image oneor more optical markers (160) coupled to a patient platform (102). Theoptical sensor (150) may be coupled to the gantry (120) such that theoptical sensor (150) rotates with the gantry (120) about the patient(114) in the patient region (140). As the gantry (120) rotates, theoptical sensor (150) may image one or more optical markers (160) fromone or more gantry angles (e.g., from the sides and from below thepatient (114)). The imaging data generated by the optical sensor (150)may be used to locate the optical marker (160) of the patient platform(102) weighted by the patient (114) relative to a reference location ofthe optical marker (160) of an unweighted patient platform (102). Thedifference in these locations corresponds to an amount of sag of thepatient platform (102). Imaging of two or more optical markers (160) mayallow the controller to determine one or more of sag, roll, and yaw ofthe patient platform (102) in a similar manner as discussed above withrespect to the elongate elements (108).

The optical marker (160) may be imaged by the optical sensor (150) togenerate optical marker (160) data having high contrast relative toother imaged elements within a bore (140) of the gantry (120) includingthe patient platform (102), patient (114), patient support element(110), and gantry housing. The image contrast allows the optical marker(160) to be spatially separated from other imaged elements such as thepatient platform (102) and the patient (114). The optical marker (160)may provide high contrast sensor data within one or more wavelengthranges of the light spectrum (e.g., visible wavelengths, infraredwavelengths, ultra-violet wavelengths). In some variations, the opticalmarker (160) may comprise a reflector configured to generate a highcontrast image using the optical sensor (150). For example, one or moreoptical markers (160) may comprise a material and/or structure toreflect light back to the optical sensor (160) with a minimum ofscattering (e.g., retroreflector). The optical marker (160) maycomprise, for example, a mirror (e.g., for reflecting light from anillumination source such as a laser) or a high contrast color surface.The optical markers (160) may have the same size, shape, number, andlocation of the radiopaque elements (e.g., elongate elements, sphere)discussed above. For example, one or more optical markers (160) may becoupled to the patient platform (102) and each optical marker (160) maycomprise a rod or spherical shape. The optical marker (160) may belocated along a longitudinal axis parallel to a longitudinal axis of thepatient platform (160).

Imaging of the optical markers (160) using an optical sensor (150) mayprovide sag determination without emission of additional beamlets (127a) from the radiation source (122) as illustrated in FIGS. 1B-1E. Sagdetermination using the optical sensor (150) and optical markers (160)may be performed concurrently with radiation therapy treatment using theradiation source (122) and multi-leaf collimator (124). In somevariations, the optical sensor (150) may comprise an infrared lightsensor and may further comprise an illumination source to enhance anamount of reflected light received from the optical marker (160). Insome of these variations, the optical sensor (150) may comprise a filterto reduce infrared data from the patient (114) and/or othernon-retroreflective sources (160). In other variations, the opticalsensor (150) may comprise a visible light sensor (e.g., charge-coupleddevice (CCD), active-pixel sensor (APS)) and may further comprise avisible light illumination source. In yet other variations, the opticalsensor (150) may comprise an ultra-violet light sensor and may furthercomprise an ultra-violet light illumination source. In some othervariations, the optical sensor (150) may comprise a time of flightrangefinder including a laser for locating one or more optical marker(160). In other variations, the optical sensor (150) may image thepatient (114) as the gantry (120) rotates to monitor a condition of thepatient (114).

In some non-limiting, exemplary variations, the patient platform (102)may have a weight capacity of about 210 kilograms and have an extensionlength from an end of the base (112) of about 2 meters. The sag ofpatient platform (102) in some instances may be several centimeters, andwill vary based on patient characteristics such as patient weight andpositioning, as well as patient platform material and design.

Conformable Patient Platform

Generally, the patient platform devices described here may provide aconformable support for a patient in imaging and/or radiotherapyprocedures. In particular, the shape of the patient platform may bepersonalized for each patient to reduce patient movement and motionartifacts during treatment and to improve patient comfort. For instance,the patient may be loaded and located outside of a gantry on the patientplatform in a patient registration process, thereby reducing setup timeof the patient platform within the gantry. This may allow more efficientscheduling of a radiotherapy system and allow more patients to receivetreatment from a radiotherapy system.

FIG. 2A is a perspective view of a variation of a conformableradiotransparent patient platform (200) comprising a conformablesubstrate (202) having a rigid base (216) coupled to a plurality ofenclosures (204). A patient (220) is depicted on the patient platform(200). It should be appreciated that the patient (220) may typicallyhave their arms at their sides during an imaging and/or treatmentprocedure. The height of each of the plurality of enclosures (204) maybe independently pressure controlled by a controller coupled to apressure source (e.g., gas, liquid) (not shown in FIGS. 2A-2B). The base(216) and enclosures (204) may be radiotransparent such that they do notinterfere with imaging and/or radiotherapy procedures. As shown in FIG.2A, the enclosures (204) may be airtight and expandable such that apressure and rigidity of the enclosures (204) may be adjustable tocomfortably and securely constrain the patient (220). FIG. 2B is aperspective view of the conformable patient platform (200) with thepatient removed to illustrate a patient contour (222).

In some variations, the enclosures (204) may comprise polyurethaneand/or other low-Z material bags or balloons that may be filled withfluid including gas and/or liquid. In other variations, the enclosures(204) may comprise a flexible membrane. In some variations, theenclosure (204) may have a diameter from about 0.001-0.050 meters, and afully-pressurized height from about 0.01-0.30 meters. For example, theenclosure (204) may have a diameter of about 0.05 meters, and afully-pressurized height of about 0.15 meters. As shown in FIGS. 2A-2B,the plurality of enclosures (204) may be cylindrical and provided in astaggered array configuration. In some variations, the plurality ofenclosures (204) may comprise a honeycomb configuration.

For an unweighted conformable substrate (202) (e.g., a conformablesubstrate (202) without a patient (220) or load applied to theenclosures (204)), the enclosures (204) may be set to a predeterminedpressure such that the enclosures (204) may comprise the same ordifferent heights. For instance, the height of the enclosures (204)along the edges of the platform (200) may be higher than other portionsto form a curve on a surface of the patient platform (200). This mayencourage a patient (220) to position themselves at a center of thepatient platform (200) or to place their heads at a predeterminedregion. In other variations, the heights of the enclosures (204) of apatient platform (200) may progressively change in order to compensatefor anticipated sag of the weighted patient platform (200). For example,an average height of the enclosures extending from a base of theplatform may increase along a longitudinal axis of the patient platform.

The number of enclosures (204) is not particularly limited, so long asthe patient (220) loaded on the platform (200) is stable and able tomaintain a constrained position. In some variations, the size anddensity of the enclosures (204) may vary over different portions of theconformable substrate (202). For instance, a lower density of largerdiameter enclosures (204) may be provided along the outer edges of thesubstrate (202) while a higher density of smaller diameter enclosures(204) may be provided for a patient head and torso area. In some ofthese instances, a third size of the enclosure (204) may be provided fora patient limb area. In this manner, the number of enclosures may beselected to optimize patient ergonomics. In some variations, otherradiotransparent support elements (e.g., cushions, pads, pillows) may becoupled to the substrate (202) to aid patient comfort and to furthersecure the patient (220) in place on the patient platform (200).

Additionally or alternatively, FIG. 2C illustrates a cross-sectionalside view of a conformable patient platform (200) comprising aconformable substrate (202) and a thermoelectric layer (210) having aheating element. In some variations, the heating element may comprise aset of very thin wires, such as having a human hair thickness. Theconformable substrate (202) may further comprise a pressure sensor (206)coupled to the conformable substrate (202) and configured to measure apressure of the conformable substrate (202). For instance, the pressuresensor (206) may be configured to measure a plurality of enclosure (204)pressures. A pressure source (208) may be coupled to each of theplurality of enclosures (204) of the conformable substrate (202) via apressure channel (214). The pressure channel (214) may comprise aradiotransparent material and may, for example, comprise a plurality oftubes coupled to corresponding enclosures (204) through the base (216).In some variations, the pressure source (208) may comprise one or moreof a pneumatic source (e.g., compressed gas). As discussed in furtherdetail below, the controller (218) may independently control a height ofeach of the plurality of enclosures (204) using the pressure sensor(206) and pressure source (208).

The thermoelectric layer (210) may be provided between the patient (220)and plurality of enclosures (204). In some variations, thethermoelectric layer (210) may be about 1.0-5.0 mm thick, and forexample, about 2.0-3.0 mm thick. One or more thermoinsulating layers(212) may be provided above and/or below the thermoelectric layer (210)to insulate either the patient (220) and/or conformable substrate (202)from heat generated by the thermoelectric layer (210). In somevariations, the thermoinsulating layer (212) may be about 1.0-15.0 mmthick. In some instances, the thermoinsulating layer (212) may be about5.0-10.0 mm thick. Heating of the thermoelectric layer (210) maytransition the thermoelectric layer (210) into a compliant configurationbased on temperature. In some variations, the thermoelectric layer (210)may transition into the compliant configuration at about 80° C. In somevariations, the thermoelectric layer (210) may be heated throughelectric current provided by an electrical conductor (e.g., metal wires)coupled to the thermoelectric layer (210). In some instances, thethermoelectric layer (210) may reach the compliant configuration inabout a minute. The compliant configuration may be pliable to conform toa patient's body shape and the rigid configuration may fix the shape andcontour of the thermoelectric layer (210). In some variations, one ormore of the thermoelectric layer (210) and thermoinsulating layer (212)may comprise a cooling element to cool and rigidize the thermoelectriclayer (210) after a patient (220) has adjusted the patient platform(200) to a desired level of comfort. For example, a cooling element maycomprise a lumen (e.g., a channel) through which a fluid (e.g., air,water) may travel through to cool the thermoelectric layer (210). Insome variations, the thermoelectric layer (210) may not span across theentire surface area of the patient platform (202) and may comprise apatient body outline.

One variation of a patient platform adjustment process using the patientplatform (200) of FIG. 2C may include the step of filling the pluralityof enclosures (204) to a set of predetermined pressures based on apreviously determined patient configuration. In some variations, the setof pressures may be between about 1-2 atm. The thermoelectric layer(210) may be heated to form a compliant configuration that may conformto a patient's body (e.g., a load applied to the enclosures). A patient(220) may then lay onto the patient platform (200) where the heights ofthe enclosures (204) may equalize and the conformable substrate (202)may conform to the patient (220).

Thereafter, the height of each of the plurality of enclosures (204) maybe adjusted for patient comfort by increasing or decreasing pressurefrom the pressure source (208) using the controller (218). The heatingelement may be deactivated so that the thermoelectric layer (210) coolsdown to form a rigid configuration that may comfortably and securelyconstrain the patient (220) generally in less than 60 seconds. In someof these variations, a cooling element of one or more of thethermoelectric layer (210) and thermoinsulating layer (212) may beactivated to more quickly transition the thermoelectric layer from thecomplaint configuration to the rigid configuration.

Once a desired shape of the patient platform (200) has been achieved,the controller (218) may store a patient configuration in memory, whenthe patient configuration comprises at least one of the pressure and/orheight of each of the plurality of enclosures (204). Accordingly,individualized patient configurations may be provided for each patient(220) to reduce the setup time of patient registration and increaseimaging and/or treatment consistency. Furthermore, the patientconfiguration may be transferable between patient platforms of differentradiotherapy systems to increase the consistency of patient positioningin imaging and/or treatment procedures across various systems. It shouldbe appreciated that the patient platforms (200) discussed herein may beparticularly useful for improving ergonomics and compliance forradiation therapy procedures requiring more time and/or higher doseaccuracy.

In some non-limiting, exemplary variations, the enclosures (204) maycomprise one or more shapes including a cylinder, cuboid, triangularprism, hexagonal prism, polygonal prism, and the like. In somevariations, different fluids (e.g., gas, liquids) and combinations offluids may be used to fill different sets of enclosures (204).

Although FIG. 2C illustrates the thermoelectric layer (210) andenclosures (204), the conformable substrate (202) may comprise thethermoelectric layer (210) without the enclosures (204) or theenclosures (204) without the thermoelectric layer (210).

Telescoping Patient Platform

Generally, the patient platform devices described here may be configuredto coordinate movement of a patient platform with emission of imagingand/or treatment beams. For example, the movement and positioning of arigid lower portion of the patient platform may be controlled to avoidintersection with an imaging and/or treatment beam. Meanwhile, aradiotransparent upper portion of the patient platform may be controlledto intersect the imaging and/or treatment beam. This spatial andtemporal control of the patient platform and beam(s) may allow movementof the rigid portion into a patient region of the gantry withoutnegatively impacting or otherwise interfering with an imaging and/ortreatment beam. Accordingly, a length of a radiotransparent portion maybe reduced such that patient platform sag may be reduced. As discussedin further detail below, the rigid lower portion and radiotransparentupper portions of the patient platform may either move relative to eachother (FIGS. 3A-3B) or maintain their positions relative to each other(FIGS. 3C-3D).

In one variation, FIGS. 3A-3B illustrate a patient platform (301) havinga rigid portion and a radiotransparent portion that may move relative toeach other. FIGS. 3A-3B are cross-sectional side views of a telescopingpatient platform system (300). The system (300) may comprise a patientplatform (301) having an upper portion (302) coupled to a lower portion(304). The upper portion (302) may be configured to move axially alongthe X-axis relative to the lower portion (304). In some variations, theupper portion (302) may be radiotransparent and the lower portion (304)may be radiopaque. A base (306) may be coupled to the lower portion(304) of the patient platform (301). The lower portion (304) may beconfigured to move relative to the base (306). Accordingly, the patientplatform (301) may telescope axially as it is extended into and out of apatient region of a gantry (310). In some variations, the upper portion(302) may comprise a set of rails coupled to a drive mechanism (e.g.,single motor) configured to move the upper portion (302) relative to thelower portion (304). Similarly, the lower portion (304) may comprise aset of rails coupled to a drive mechanism configured to move the lowerportion (304) relative to the base (306).

In some variations, the upper portion (302) and lower portion (304) mayhave different radiotransparency. For instance, the upper portion (302)may be radiotransparent and less rigid relative to the lower portion(304) that may be radiopaque and have more rigidity.

The system (300) may further comprise a gantry (310) having an imagingradiation source (320) and a treatment radiation source (330). Forexample, the imaging radiation source (320) may be a kV radiation sourceand the treatment radiation source (330) may be a MV radiation source.The treatment radiation source (330) may be coupled to a multi-leafcollimator (332) and may be located opposite a detector (336). Thetreatment radiation source (330) may be configured to emit a treatmentbeam (334) in a treatment beam plane perpendicular to a longitudinalaxis of the patient platform (301). The imaging radiation source (320)may be configured to emit an imaging beam (322) in an imaging beam planeperpendicular to a longitudinal axis of the patient platform (301),where transmission of the imaging beam (322) through the patient may bedetected by an imaging detector (337). Although FIG. 3A depicts both theimaging beam (322) and the treatment beam (334) as being emittedsimultaneously, thereby treating one region of the patient while imaginganother region of the patient, it should be understood that each ofthese beams may be activated sequentially or separately. That is,imaging of the patient using the imaging beam (322) need not take placewhile the patient is being treated with the treatment beam (334) (e.g.,the imaging beam (332) and the treatment beam (334) are not activated atthe same time).

With respect to an imaging procedure, the system (300) may be in animaging configuration, an example of which is depicted in FIG. 3A. Asshown there, a controller (340) may be configured to move the rigidlower portion (304) (that may be radiopaque) as close to the imagingbeam (322) as possible without intersecting the imaging beam (322). Aleading edge of the lower portion (304) may be separated by a firstdistance from a plane of the imaging beam (322). In some variations, thefirst distance may be about 2 centimeters. In this manner, the stifferportion of the patient platform (301) may be moved as close as possibleto the imaging beam (322) without interfering with the imaging beam(322). The upper portion (302) may be moved (telescoped) freely in anaxial direction relative to the lower portion (304) to intersect theimaging beam (322) and image a desired region the patient (not shown).

As shown in FIG. 3A, a controller (340) of the system (300) may beconfigured to move the upper portion (302) and lower portion (304) suchthat the lower portion (304) is non-intersecting with the imaging planeof the imaging beam (322) and the upper portion (302) intersects theimaging plane of the imaging beam (322). In this manner, only theradiotransparent upper portion (302) intersects the imaging beam (322).

With respect to a radiotherapy procedure, the system (300) may bedisposed in a treatment configuration, an example of which is depictedin FIG. 3B. As shown there, the controller (340) may be configured tomove the rigid lower portion (304) (that may be radiopaque) as close tothe treatment beam (334) as possible without intersecting the treatmentbeam (334). In this manner, the stiffer portion of the patient platform(301) may be moved as close as possible to the treatment beam (334)without interfering with the treatment beam (334). In some variations,the lower portion (304) may be positioned (e.g., by a drive mechanism)such that a leading edge of the lower portion (304) may be located at apredetermined second distance away from the treatment plane (FIG. 3B).For example, the second distance may be about 2 centimeters. The upperportion (302) may be moved (telescoped) freely in an axial directionrelative to the lower portion (304) to intersect the treatment beam(334) and treat the patient (not shown). In the treatment configurationdepicted in FIG. 3B, the imaging radiation source (320) may not beactivated because the rigid lower portion (304) (that may be radiopaque)is located in the beam path of the imaging radiation source (320).

As shown in FIG. 3B, a controller (340) of the system (300) may beconfigured to move the upper portion (302) and lower portion (304)(e.g., by a drive mechanism) such that the lower portion (304) isnon-intersecting with the treatment plane of the treatment beam (334)and the upper portion (302) intersects the treatment plane of thetreatment beam (334). In this manner, only the radiotransparent upperportion (302) intersects the treatment beam (334).

FIGS. 3C-3D illustrate cross-sectional side views of another variationof a patient platform system (350) comprising a patient platform (351)having a rigid portion and a radiotransparent portion that maintaintheir positions relative to each other. The system (350) may comprise apatient platform (351) having an upper portion (352) fixed relative to alower portion (354). For instance, a length of a cantilevered portion ofthe upper portion (352) is constant in FIGS. 3C-3D. In some variations,the upper portion (352) may be radiotransparent and the lower portion(354) may be radiopaque. A base (356) of the patient platform (351) maybe coupled to the lower portion (354) and configured to control a heightand/or pitch of the patient platform (351). The lower portion (354) maybe movable with respect to the base (356) such that the patient platform(351) may move relative to the base (356). Accordingly, the patientplatform (351) may telescope in an axial direction with respect to thebase (356) as it is extended into and out of a gantry (310). The lowerportion (354) may be made of any material that is sufficiently rigidsuch that regardless of the length of the lower portion (354) that maybe cantilevered from the base (356) (e.g., FIG. 3D), the lower portion(354) does not sag with respect to the base (356). Additionally oralternatively, the lower portion (354) may be made of any material thatis more rigid than the material of the upper portion (352).

Since the upper portion (352) may be fixed relative to the lower portion(354), it should be appreciated that a patient (not shown) laying on thepatient platform (351) may cause constant sag to the patient platform(351) (assuming the patient does not move). Consequently, the sag of thepatient platform (351) may comprise a set of known values across alength of the patient platform (351). That is, the sag of the patientplatform at a particular region of interest of a patient may bedetermined prior to and/or at the start of a treatment session andremain the same throughout the session, regardless of how the platform(352) moves with respect to the base (356). Furthermore, by fixing theupper portion (352) to the lower portion (354), the patient platform(351) illustrated in FIGS. 3C-3D may be simpler to manufacture than thepatient platform (301) illustrated in FIGS. 3A-3B.

With respect to an imaging procedure, the system (350) may be in animaging configuration, an example of which is depicted in FIG. 3C. Asshown there, a controller (340) may be configured to move the lowerportion (354) (that may be radiopaque) as close to the imaging beam(322) as possible without intersecting the imaging beam (322). In thismanner, the radiopaque portion of the patient platform (351) may bemoved as close as possible to a path of the imaging beam (322) withoutinterfering with the imaging beam (322). In some variations, the lowerportion (354) may be positioned such that a leading edge of the lowerportion (354) may be located at a predetermined first distance away fromthe imaging plane (FIG. 3C). For example, the first distance may beabout 2 centimeters. The upper portion (352) may intersect the imagingbeam (322) to image a desired region of the patient (not shown).

As shown in FIG. 3C, a controller (340) of the system (350) may beconfigured to move the upper portion (352) and lower portion (354) suchthat the lower portion (354) is non-intersecting with the imaging planeof the imaging beam (322) and the upper portion (352) intersects theimaging plane of the imaging beam (322). In this manner, only theradiotransparent upper portion (352) intersects the imaging beam (322).

With respect to a radiotherapy procedure, the system (350) may bedisposed in a treatment configuration, an example of which is depictedin FIG. 3D. As shown there, the controller (340) may be configured tomove the rigid lower portion (354) (that may be radiopaque) as close tothe treatment beam (334) as possible without interfering with thetreatment beam (334). In this manner, the lower portion (354) of thepatient platform (351) may be moved as close as possible to thetreatment beam (334) without receiving a radiation dose. In somevariations, the lower portion (354) may be positioned such that aleading edge of the lower portion (354) may be located at apredetermined second distance away from the treatment plane (FIG. 3D).For example, the second distance may be about 2 centimeters. The upperportion (352) may intersect the treatment beam (334) to treat thepatient (not shown). In the treatment configuration depicted in FIG. 3D,the imaging radiation source (320) may not be activated because therigid lower portion (354) (that may be radiopaque) is located in thebeam path of the imaging radiation source (320).

As shown in FIG. 3D, a controller (340) of the system (350) may beconfigured to move the patient platform (351) such that the lowerportion (354) is non-intersecting with the treatment plane of thetreatment beam (334) and the upper portion (352) intersects thetreatment plane of the treatment beam (334). In this manner, only theradiotransparent upper portion (352) intersects the treatment beam(334).

In some non-limiting, exemplary variations, the upper portion (302, 352)may comprise radiotransparent carbon fiber and the lower portion (304,354) may comprise radiopaque aluminum or other stiff, low-Z materials.In these variations, the aluminum portion of the patient platform (301,351) may be configured to sag less than the carbon fiber portion (302,352). In some variations, the lower portion (304, 354) may be thickerthan the upper portion (302, 352). In some variations, the lower portion(304, 354) may have a height of about 0.02-0.50 meters and the upperportion (302, 352) may have a height less than the lower portion (302,354). In some variations, the patient platform (300, 350) described maycomprise a vertical drive system (e.g., scissor elements) as describedin detail with respect to FIGS. 4A-4E.

Adjustable Patient Platform

Generally, the patient platform devices described here may provide aplurality of degrees of freedom to move a patient on a patient platformto a desired position and orientation with respect to a radiotherapytreatment beam. As shown in FIGS. 4A-4C and 4F, a patient platform (401)may provide at least one of axial, lateral, and vertical translation, aswell as pitch and/or yaw rotation.

FIGS. 4A-4B and 4D are side views and FIGS. 4C, 4E, and 4F areperspective views of a system (400) comprising a radiotransparentpatient platform (401) coupled to a base (420). The base (420) may beprovided external to a patient region of a gantry (not shown forclarity) and may not be radiotransparent. The patient platform (401) maycomprise an upper portion (402) and a lower portion (404). The upperportion (402) is not drawn to scale (e.g., the upper portion (402) isrelatively short in FIG. 4A) for the sake of illustration. A pivot (412)may couple the upper portion (402) of the patient platform (401) to thelower portion (404) of the patient platform (401). In some variations,the pivot (412) may comprise a set of curved rails (e.g., two). Itshould be appreciated that the pivot (412) may allow the upper portion(402) of the patient platform (401) to rotate about the Z-axis (414)without interfering with either an imaging or treatment beam.

In some variations, one or more of an axial drive system (440), lateraldrive system (450), vertical drive system (460), pitch drive system(470), and yaw drive system (410) may be coupled to the patient platform(401). For example, the axial drive system (440) may be coupled betweenthe lower portion (404) and the lateral drive system (450), the lateraldrive system (450) may be coupled between the axial drive system (440)and the yaw drive system (410), the yaw drive system (410) may becoupled between the lateral drive system (450) and the pitch drivesystem (470), and the pitch drive system (470) may be coupled betweenthe yaw drive system (410) and the upper portion (402). Thisconfiguration allows the axial drive system (440), lateral drive system(450), pitch drive system (470), and yaw drive system (410) to moveaxially relative to the vertical drive system (460) such that movementof the vertical drive system (460) may be independent of the other drivesystems.

In some variations, the system (400) may comprise a controller (notshown) comprising a processor and memory configured to control one ormore of the lateral drive system (450), vertical drive system (460),pitch drive system (470), and yaw drive (410). In some variations, theaxial drive system (440), lateral drive system (450), and pitch drivesystem (470) may each comprise a pair of linear rails driven by a singlemotor (e.g., leadscrew drive, linear motor). The axial drive system(440) may comprise an axial drive element (442) coupled to the lowerportion (404) of the patient platform (401). A pair of axial rails (444)may be coupled to the axial drive element (442). The axial drive system(440) may be configured to move the upper portion (402) in an axialdirection (along the X-axis) relative to the lower portion (404) bymoving the upper portion (402) along the axial rails (444). In somevariations, the axial drive element (442) may comprise a rotary motorcoupled to a leadscrew and/or drive belt that are in turn coupled to theaxial rails (444). For example, the axial drive element (442) maygenerate a motor continuous peak torque of up to about 0.5 Nm. In othervariations, the axial drive element (442) may comprise a linear motorcoupled to the axial rails (444). In some variations, the axial rails(444) may be spaced apart from each other between about 35 cm and 55 cm.A cross-sectional width of each rail (444) may be between about 15 mmand about 30 mm. In some variations, the axial drive system (440) may beconfigured to axially translate the upper portion (402) relative to thelower portion (404) in a range of up to about 200 cm.

The lateral drive system (450) may comprise a lateral drive element(452) coupled to the patient platform (401). A pair of lateral rails(454) may be coupled to the lateral drive element (452). The lateraldrive system (450) may be configured to move the upper portion (402) ina lateral direction (along the Y-axis) relative to the lower portion(404) by moving the patient platform (401) along the lateral rails(454). For example, FIGS. 13A-13C illustrate a patient platform (1310)moving in a lateral direction (along the Y-axis) within a gantry (1330).The lateral rails (454) may be disposed perpendicular to the axial rails(444). The lateral drive element (452) may generate a motor continuouspeak torque of up to about 0.5 Nm. In some variations, the lateral rails(454) may be spaced apart from each other between about 45 cm and about75 cm. A cross-sectional width of each rail (454) may be between about15 mm and about 30 mm. In some variations, the lateral drive system(450) may have a lateral range of motion of up to about 200 cm.

The pitch drive system (470) coupled to the patient platform(401) may beconfigured to raise and/or lower an end of an upper portion (402) so asto pitch the upper portion (402) about a pitch pivot (478). A pitchdrive element (472) may be coupled to one or more wedges (474) tovertically translate an end of the upper portion (402). In somevariations, the pitch drive system (470) may comprise a pitch driveelement (472) coupled to the patient platform (401). In some variations,the pitch drive system (470) may comprise a pair of wedges (474) coupledto the pitch drive element (472) via a pitch linear screw (476). Thepitch drive system (470) may be configured to pitch the patient platform(401) about a pitch pivot (478) (about the Y-axis). For example, thepitch drive element (472) and screw (476) may drive one of the twowedges (474) laterally (along the Y-axis) such that the second of thetwo wedges (474) is pushed upward (along the Z-axis). Pushing the secondwedge upward may tilt the upper portion (402) of the patient platform(401) such that a first end of the upper portion (402) of the patientplatform (401) (to which the wedges (474) are coupled) is higher than asecond end of the upper portion (402) of the patient platform (474).Rotation about the pitch pivot (478) enables the pitching, or tilting,of the upper portion (402) of the patient platform (474) relative to ahorizontal plane (e.g., the X-Y plane and lower portion (404) plane).

FIG. 4F is a perspective view of a variation of a pitch drive system(470) as depicted in FIG. 4C. In particular, the pitch drive element(472) may comprise a motor (471) comprising a toothed belt coupled tothe pitch linear screw (476). For example, the motor (472) may becoupled to a first linear screw (476 a) and a second linear screw (476b). The first and second linear screws (476 a, 476 b) may be coupled torespective portions of a first wedge (474 a) (e.g., lower wedge). Eachportion of the first wedge (474 a) may be coupled to a pair oflaterally-oriented linear rails. The first wedge (474 a) may movesymmetrically laterally via the screw (476) such that the two portionsof the first wedge (474 a) simultaneously move towards or away from eachother.

The wedge (474) may further comprise a second wedge (474 b) (e.g., upperwedge) slidably coupled to the first wedge (474 a) via a set of linearrails. For example, the first wedge (474 a) may comprise a first angledsurface (477) disposed facing a second angled surface (479) of acorresponding second wedge (474 b). The second angled surface (479) maycomprise a set of linear rails on which the first wedge (474 a) slides.Lateral motion of the first wedge (474 a) may be thus translated tovertical motion of the second wedge (474 b) and upper portion (402) suchthat the upper portion (402) may pitch. In some variations, the pitchdrive system (470) may pitch up a proximal end of the upper portion(402) by up to about 5 degrees and pitch down the upper portion (402) byup to about 3 degrees. In some variations, a change in pitch of theupper portion (402) may be used to counteract sag of the cantileveredend of the upper portion (402).

In some variations, each portion of the first wedge (474 a) may comprisea width of between about 200 mm and about 250 mm, a length of betweenabout 60 mm and about 120 mm, and a height of between about 25 mm andabout 75 mm. For example, each portion of the first wedge (474 a) maycomprise a width of about 220 mm, a length of about 90 mm, and a heightof about 50 mm. In some variations, a first angled surface (477) maycomprise an angle of between about 30 degrees and about 50 degreesrelative to the horizontal plane (i.e., X-Y plane). For example, thefirst angled surface (477) may comprise an angle of about 38 degrees.

In some variations, each portion of the second wedge (474 b) maycomprise a width of between about 40 cm and about 60 cm, a length ofbetween about 50 mm and about 150 mm, and a height of between about 10cm and about 30 cm. For example, each portion of the second wedge (474b) may comprise a width of about 50 cm, a length of about 10 cm, and aheight of about 20 cm. In some variations, a second angled surface (479)may comprise an angle of between about 130 degrees and about 150 degreesrelative to the horizontal plane (i.e., X-Y plane). For example, thesecond angled surface (479) may comprise an angle of about 142 degrees.

As shown in FIGS. 4A-4C, the vertical drive system (460) in somevariations may comprise a pair of scissor elements (462) andcorresponding cylinders (468) (e.g., hydraulic, pneumatic) coupled tothe patient platform (401). The vertical drive system (460) may beconfigured to move the patient platform (401) in a vertical direction(along the Z-axis) relative to the base (420). Vertical movement of thepatient platform (401) may be independent of other translational and/orrotational movement provided by the axial drive system (440), lateraldrive system (450), pitch drive system (470), and yaw drive system(410). A vertical drive element (464) may be coupled to the scissorelements (462) through one or more linear screws (466) and configured toraise and/or lower the patient platform (401). One or more cylinders(468) may be configured to generate an upward force to assist thevertical drive element (464) and move the patient platform (401). Insome of these variations, one or more of the cylinders (468) may bepivotally coupled to the base (420) and the lower portion (404) of thepatient platform (401). The scissor element (462) may comprise a firstarm (463) and a second arm (465) coupled to each other about a pivotpoint (467). The pivot point (467) may couple an intermediate portion ofthe first arm (463) to an end portion of the second arm (465). The otherend of the second arm (465) may pivotally couple to the base (420). Anend of the first arm (463) may pivotally couple to the lower portion(404). The other end of the first arm (463) may pivotally couple to atrack (469) of the base (420) such that the first arm (463) may slideaxially along the track (469) (along the X-axis). A track (469) may beprovided for each of the first arms (463). As shown in FIGS. 4C and 4E,some variations of the vertical drive system (460) may comprise fourpairs of first and second arms (463, 465) with two pairs disposed ateach of the ends of the base (420) and lower portion (404). The scissorelements (462) shown in FIGS. 4A-4C may comprise a mirror configuration.In some variations, the vertical drive system (460) may be located at afixed position outside of a gantry while the other drive systems maytranslate axially relative to the gantry.

FIGS. 4A and 4C illustrate a vertical drive element (464) comprising twolinear screws (466) configured to drive the pair of scissor elements(462) disposed at each end of the patient platform (400). As thevertical drive element (464) drives one or more of the linear screws(466) axially (along the X-axis) away from the vertical drive element(464), the lower portions of the first arms (463) may be brought closerto their respective second arms (465) such that the height of thescissor element (462) and lower portion (404) is increased. Conversely,the vertical drive element (464) may decrease a height of the lowerportion (404). The patient platform (400) may be pitched (e.g., tilted)when the linear screws (466) are driven unequally. In some variations,the first arms (463) may comprise a length of between about 60 cm andabout 100 cm, and the second arms (465) may comprise a length of betweenabout 30 cm and about 60 cm. In some variations, the track (469) maycomprise a length of between about 50 cm and about 90 cm. In somevariations, the vertical drive system (460) may comprise a verticalrange of motion of up to about 60 cm.

In some variations, as shown in FIGS. 4D and 4E, the vertical drivesystem (460) may comprise a pair of scissor elements (462) in a parallelconfiguration. That is, each of the first arms (463) in the parallelconfiguration face the same direction and are parallel to each other.Likewise, each of the second arms (465) face the same direction and areparallel to each other. This configuration of scissor elements mayreduce a size and/or simplify the vertical drive element (464). Avertical drive element (464) may be directly coupled to one pair ofscissor elements (460) via a linear screw (466) at one end of thepatient platform. The pairs of scissor elements (462) at each end of thepatient platform (400) may be coupled via a linkage (461). For example,the linkage (461) may couple the first arms (463) at each end of thepatient platform (400) to each other. This allows the vertical driveelement (464) to drive each of the scissor elements (462) simultaneously(e.g., together) using one linear screw (466) rather than providing alinear screw for the scissor elements at each end of the patientplatform (400). As the vertical drive element (464) drives (e.g.,rotates) the linear screw (466) axially (along the X-axis) away from thevertical drive element (464), the lower portions of the first arms (463)may be brought farther away from their respective second arms (465) suchthat the height of the scissor element (462) and lower portion (404) isdecreased. In some variations, the vertical drive element (464) maycomprise a pneumatic element, an electromechanical element, or hydraulicelement. In some variations, the cylinder (468) may further comprise oneor more cylinders as described with respect to FIGS. 4A-4C.

The yaw drive system (410) may be coupled to the upper portion (402) ofthe patient platform (401). The yaw drive system (410) may comprise ayaw drive element and be configured to yaw (rotate) the upper portion(402) of the patient platform (401) relative to the lower portion (404)of the patient platform (401) about a pivot axis (414) of pivot (412) bymoving the patient platform (401) along the curved rails (412). In somevariations, the curved rail may provide a stiff base and comprise alength of about 1.0 cm and about 10.0 cm. In some variations, the curvedrails (412) may comprise a radius of between about 25 cm and about 35cm, and be spaced apart between about 50 cm and about 70 cm. In somevariations, the yaw drive system (410) may provide a range of motion ofup to about 25 degrees.

The lower portion (404) of the patient platform (401) depicted in FIG.4A does not yaw. In some variations, the patient platform (401) maycomprise a handle (480) for an operator to manually adjust a position ofthe patient platform (e.g., adjust an axial position and/or lateralposition). It should be noted that the system (400) described above maybe used in conjunction with any of the methods corresponding to FIGS. 12and 13A-13E described and illustrated below. In some variations, thesystem (400) as described herein may be used to move the patientplatform as described in detail herein, such as with respect to themethods described in FIGS. 13A-13E.

In some variations, one or more portions of the patient platform (401)may comprise carbon fiber due to its radiotransparency and ability toprovide rigid support to a patient. In some variations, the patientplatform (401) may have a length of about 1.5 m and about 3.0 m, a widthof about 0.50 m and about 2.0 m, and a thickness of about 0.05 m andabout 0.50 m, and may preferably have a length of about 2 m, a width ofabout 0.50 m, and thickness of about 0.10 m. In some variations, thepatient platform (401) may have a weight capacity of about 210 kilogramsand have an extension length from an end of the base (112) of about 2 m.In some variations, the patient platform (401) may comprise one or moreof the elongate elements and/or bores as described in detail herein withrespect to FIGS. 1A-1F. In some variations, the patient platform (401)may comprise a conformable substrate as described in detail herein withrespect to FIGS. 2A-2C.

Phantom

Generally disclosed herein are patient platforms comprising a phantomfor use in calibrating one or more components of a radiotherapy system.For example, a radiotherapy system may comprise a rotatable gantry, oneor more radiation detectors mounted on the gantry, a radiation source(e.g., linac) mounted on the gantry, and a beam-shaping assemblydisposed in the radiation beam path of the radiation source. Thebeam-shaping assembly may comprise one or more sets of jaws and/orcollimators. Additionally or alternatively, some radiotherapy systemsmay comprise an imaging system, such as a CT system, that may be used toacquire CT images. The radiation detector may receive a beam emittedthrough the phantom from the radiation source. The phantom may comprisea plurality of types of radiation detectors and may be used tocharacterize, verify, and/or calibrate the expected or desired functionof the radiation source, multi-leaf collimator, radiation detector, aswell as to verify performance of dose delivery and dose calculationalgorithms. The data generated by one or more of these dosimeters may beused for quality assurance procedures. For example, a daily qualityassurance procedure may quickly generate dose data using two beamsemitted through two water-filled steps of different depths forcalibration of a radiation detector. Another quality assurance procedure(e.g., weekly, monthly, quarterly) may use a plurality of beams emittedthrough a plurality of radiation detectors (e.g., water-filled steps,ionization chambers, radiographic film). Generating a larger set of dosedata from a plurality of radiation detector types may increase theaccuracy of the dose data and subsequent verification and/or calibrationby allowing cross-calibration of dose data generated by different typesof radiation detectors (e.g., ionization chambers, radiographic sheets,etc.). In some variations, the phantom may be mounted to an underside ofa patient platform at a predetermined location that allows forconvenient storage outside of a patient treatment region of a patientplatform. In particular, the location of the phantom underneath and awayfrom the patient treatment region allows a patient to be disposed on apatient support surface of the patient platform and receive radiotherapytreatment without interference from the phantom. In other words, aportion of the space underneath the patient platform may be efficientlyused to mount the phantom without altering a radiotherapy procedureusing the patient platform.

FIGS. 16A-16B depict cross-sectional side views of some variations of aphantom (1602). For example, FIG. 16A depicts a radiotherapy system(1600) comprising a patient platform (1620) and a phantom (1602) coupled(e.g., mounted) to an underside of the patient platform. The patientplatform (1620) may have a patient support surface configured to hold apatient thereon (e.g., side facing the radiation source (1630) in FIG.16A) with the underside surface disposed opposite the patient supportsurface (e.g., side facing the radiation detector (1640) in FIG. 16A).The patient platform (1620) is not drawn to scale (e.g., the patientregion (1650) is relatively short in FIG. 16A) for the sake ofillustration. A radiation source (1630) and a radiation detector (1640)may be disposed on a gantry (not shown for the sake of clarity) andpositioned relative to the patient platform (1620) to generate a beampath that intersects the patient platform (1620) and phantom (1602). Thephantom (1602) may be disposed within a phantom region (1660) of thepatient platform (1620) that is outside a patient region (1650). Thatis, the patient region (1650) and not the phantom region (1660) may bepositioned to intersect a beam plane of the radiation source (1630)during a treatment session. The patient platform (1620) may be advancedsuch that the beam plane intersects the phantom region (1660) onlyduring a quality assurance procedure. The phantom (1602) may comprise ahousing having an internal volume configured for liquid such as water.For example, the housing may define an internal fluid-tight volume. Thehousing may comprise a material such as acrylic (e.g.,polymethylmethacrylate (PMMA)) that may be dosimetrically similar towater.

As shown in FIG. 16A, the housing of the phantom (1602) may comprise aplurality of steps (1604) arranged along a longitudinal axis (e.g.,X-axis) of the phantom (1602). Each step may have a correspondingpredetermined depth. The system (1600) may be configured to deliver apredetermined radiation dose to one or more of the steps such thatdelivered dose measurements may be compared to reference dose data(e.g., expected dose measurements) for each of the steps. Differencesbetween the measured dose and expected dose may be used for calibrationof one or more components of the system (1600). The phantom (1602) maycomprise two or more steps such that the detector (1630) may generatedose data corresponding to at least two step depths of the phantom whenrespective beams (1632) pass through each step. The dose data atdifferent step depths may be used for absolute and/or relative dosimetrycalculations. In some variations, dose data generated by the detector(1640) using the steps (1604) may be calibrated against one or more ofdose data generated using the ionization chambers (1606), dose datagenerated using radiographic films, and/or dose data generated by otherdosimeters.

In some variations, dose data may be used to calculate a tissue phantomratio (TPR) where a first point dose of radiation is measured at a firstdepth (e.g., reference depth of about 5 cm) and at least a second pointdose is measured at a second depth (e.g., about 10 cm). The TPR may beused to characterize the beam quality of a radiation source and pointdose measurements at a plurality of depths may be used to improve anaccuracy of the TPR value.

In some variations, the phantom (1602) may comprise 2, 3, 4, 5, 6, 7, ormore steps. For example, the phantom (1602) may comprise five or sixsteps of the same material (e.g., water). In some variations, the stepsmay have different materials. For example, each step may comprisedifferent densities and/or attenuation characteristics. Each step maycomprise a depth (i.e., along the Z-axis) of at least about 1 cm andabout 4 cm or more when filled with water. The phantom (1602) maycomprise a width (i.e., along the Y-axis) of at least about 2 cm. Eachstep (1604) may have a length of between about 2 cm and about 5 cm. Forexample, a phantom (1602) comprising six steps may have a depth ofbetween about 25 cm and about 40 cm. Each step (1604) of the phantom(1602) may comprise a plateau in parallel with a longitudinal axis(i.e., X-axis) of the phantom (1602). In other variations, the steps(1604) of the phantom (1602) may be spaced apart along the lateral axis(i.e., Y-axis) of the patient platform (1620). Although the steps (1604)depicted in FIG. 16A correspond to a monotonic function and resemble aset of stairs, the steps (and their corresponding depths) may be orderedand spaced along the longitudinal axis of the phantom in any desiredconfiguration.

The phantom (1602) may further comprise a plurality of radiationdetectors (e.g., ionization chambers and dosimeter slots). In somevariations, each of the radiation detectors (1606, 1608) may be disposedat the predetermined depth of its corresponding step (1604). In somevariations, the phantom (1602) may comprise one or more radiationdetectors including a gas-filled radiation detector such as anionization chamber (1606). The ionization chamber (1606) may comprise anair chamber having an anode-cathode electrode pair. The electrode pairmay be coupled to an electrometer and power supply (not shown in FIG.16A). A voltage potential applied between the electrode pair maygenerate an electric field in the chamber (1606). When the gas in thechamber is ionized by a radiation beam (1632) emitted from the radiationsource (1630), the resultant ionization current generated in theionization chamber (1606) may be measured by the electrometer. Theionization current may be proportional to a radiation dose received bythe ionization chamber and used for absolute and/or relative dosimetry.Accordingly, absolute dose of the beam (1632) may be calculated and usedto calibrate the system (1600) (e.g., radiation source (1630)).

As shown in FIG. 16A, each of the ionization chambers (1606) anddosimeter slots (1608) may be substantially in a plane of itscorresponding step (1604). That is, each of the ionization chambers(1606) may be disposed at the predetermined depth of its correspondingstep (1604) along a longitudinal axis of the phantom (1602). This allowsdose data generated using the ionization chambers (1606) to becalibrated against one or more of dose data generated using the stepsand radiation detector (1640), dose data generated using radiographicfilms, and/or dose data generated using other dosimeters. For example,dose data generated from an electrometer coupled to the ionizationchambers (1606) may be used to calculate absolute dose at apredetermined depth of the phantom (1602). In some variations, theionization chamber (1606) may comprise a parallel-plate chamber,cylindrical chamber, well-type chamber, free-air chamber, ventedchamber, sealed chamber, combinations thereof, and/or the like.

As shown in FIG. 16B, ionization chambers (1606) in some variations maybe arranged along a longitudinal axis (i.e., X-axis) of the phantom(1602) and along a vertical axis (i.e., Z-axis). In this manner, beams(1632) emitted parallel to the Z-axis may intersect a single ionizationchamber without interference from another ionization chamber, thusreducing cross-talk and/or cavity effects due to attenuation changesfrom gas within another ionization chamber. In some variations, theplurality of ionization chambers (1606) may be within 5 mm of each otheralong the longitudinal axis (i.e., X-axis).

As shown in FIG. 16A, each of the dosimeter slots (1608) may be disposedat the predetermined depth of its corresponding step (e.g.,substantially in a plane of its corresponding step (1604)). Thedosimeter slots (1608) may be substantially parallel to the longitudinalaxis (i.e., X-axis) and arranged along the vertical axis (i.e., Z-axis).In some variations, one or more dosimeter slots may be used to measurebeam scatter of the radiation source (1630). For example, a verticaldosimeter slot (1609) may be disposed parallel or nearly parallel to thevertical axis. For example, the vertical dosimeter slot (1609) may beangled between about 2 degrees and about 10 degrees relative to thevertical axis (i.e., Z-axis). The slots (1608, 1609) may comprise one ormore shapes including rectangular, square, trapezoidal, oval orelliptical, arc-shaped (e.g., hemi-arc, hemi-spherical,hemi-cylindrical), combinations thereof, and the like. The slots (1608,1609) may define an opening having a height sufficient to hold aradiographic sheet at a predetermined depth of the phantom (1602). Insome variations, one or more radiographic sheets (e.g., radiographicfilm) may be disposed between one or more of the dosimeter slots (1608,1609). The radiographic sheets may be used to acquire radiation dosemeasurements. Data from the radiographic sheets may have a high spatialresolution and may be digitized for analysis. For example, theradiographic sheets may be used to calculate the amount of dose appliedto the phantom (1602) and/or used to generate a dose map. The dose mapmay be compared to the predicted dose to identify any dose deviations.In some variations, a calibration curve may be generated using dose datafrom the radiographic sheets. Accordingly, the operation of one or moreof the linac, gantry, and the multi-leaf collimator may be validatedand/or characterized based on the radiation dose data and/or dose mapacquired using the radiographic sheets and/or radiation detectors.

FIG. 17 depicts a cross-sectional side view of another variation of apatient platform (1720) comprising a phantom (1702) for a radiotherapysystem (1700). For example, FIG. 17 depicts a radiotherapy system (1700)comprising a phantom (1702) coupled (e.g., mounted) to an underside of apatient platform (1720). The patient platform (1720) may have a patientsupport surface configured to hold a patient thereon (e.g., the surfaceof the platform that faces the radiation detector (1740) in FIG. 17 )with the underside surface disposed opposite the patient support surface(e.g., the surface of the platform that faces the radiation source(1730) in FIG. 17 ). The patient platform (1720) may define alongitudinal axis parallel with the X-axis. The patient platform (1720)is not drawn to scale (e.g., the patient region (1750) is relativelyshort in FIG. 17 ) for the sake of illustration. A radiation source(1730) and a radiation detector (1740) may be disposed on a gantry (notshown for the sake of clarity) relative to the patient platform (1720)so as to generate a beam that intersects the patient platform (1720) andphantom (1702). The phantom (1702) may be disposed within a phantomregion (1760) of the patient platform (1720) that is outside a patientregion (1750). That is, the patient region (1750) and not the phantomregion (1760) may be positioned to intersect a beam plane of theradiation source (1730) during a treatment session. The patient regionhas a longitudinal length that is greater than the longitudinal lengthof the phantom region (FIG. 17 is not drawn to scale; the phantom regionhas been enlarged). The patient platform (1720) may be advanced suchthat the beam plane intersects the phantom region (1760) only during aquality assurance procedure. In some variations, a patient platform mayhave a patient region that is distal to the phantom region, and thepatient region and phantom region are non-overlapping.

The phantom (1702) may comprise a housing having a plurality of regionsarranged along the longitudinal axis. For example, the phantom (1702)may comprise two or more regions having different attenuationcharacteristics used to generate dose data corresponding to at least twoor more predetermined depths of a water-filled phantom when respectivebeams (1732) pass through each region. The dose data of the regions maybe used for absolute and/or relative dosimetry calculations. In somevariations, dose data generated by the detector (1740) may be calibratedagainst one or more of dose data generated using the ionization chambers(1712), dose data generated using radiographic films, and/or dose datagenerated using other dosimeters. In some variations, the densityregions (1704, 1706, 1708, 1710) may be spaced along either alongitudinal (i.e., along the X-axis) or a lateral axis (i.e., along theY-axis) of the patient platform (1720).

As shown in FIG. 17 , the phantom (1702) may comprise a first region(1704), second region (1706), third region (1708), and fourth region(1710) having respective densities (A, B, C, D). In some variations, thephantom (1702) may comprise 2, 3, 4, 5, 6, 7, or more density regions.For example, the phantom (1702) may comprise four or five regions eachhaving the same thickness, but comprising different density material. Inone variation of a phantom comprising four regions of the samethickness, the first region (1704) may comprise a mass per area of about1.5 g/cm², the second region (1706) may comprise a mass per area ofabout 5 g/cm², the third region (1708) may comprise a mass per area ofabout 10 g/cm², and the fourth region (1710) may comprise a mass perarea of about 20 g/cm². In another variation of a phantom comprisingthree regions of the same thickness, the first region (1704) maycomprise a mass per area of about 1.5 g/cm², the second region (1706)may comprise a mass per area of about 10 g/cm², and the third region(1708) may comprise a mass per area of about 20 g/cm². Alternatively,each region may have a density and thickness different from the otherregions of the phantom (1702).

Each density region may comprise a thickness (i.e., along the Z-axis) ofat least about 5 mm or more. The phantom (1702) may comprise a width(i.e., along the Y-axis) of at least about 2 cm. Each region of thephantom (1702) may have a length between about 2 cm and about 5 cm. Thevariable density regions of the phantom (1702) may comprise a materialsuch as lead, copper, steel, acrylic, tungsten, uranium, combinationsthereof, and the like. In one variation, the first region (1704) maycomprise acrylic, the second region (1706) may comprise aluminum, thethird region (1708) may comprise copper or steel, and the fourth region(1710) may comprise lead. In some variations, the region with thehighest-density material may be located at a greater distance away fromthe other regions, so that scattered radiation from the highest-densityregion does not interfere with the dose data of the other regions.

In some variations, the phantom (1702) may further comprise a pluralityof radiation detectors (1712, 1714) arranged along the longitudinalaxis. For example, as depicted in FIG. 17 , each density region (1704,1706, 1708, 1710) having a respective ionization chamber (1712) anddosimeter slot (1714). The ionization chamber (1712) and dosimeter slot(1714) may be similar to those described herein with respect to FIGS.16A-16B. In some of these variations, a dosimeter slot (1714) may bearranged to intersect its corresponding ionization chamber (1712). Insome of these variations, an ionization chamber plug may be insertedinto the ionization chamber (1712) when a radiographic sheet is loadedinto the dosimeter slot (1714) and the ion chamber (1710). In othervariations, the dosimeter slot (1714) and ionization chamber (1712) of adensity region (1704, 1706, 1708, 1710) may be spaced apart along thelongitudinal and/or lateral axis. In some variations, the radiationdetectors (1712, 1714) may be disposed in a region of the phantom (1702)comprising a material such as acrylic (e.g., polymethylmethacrylate(PMMA)) that may be dosimetrically similar to water. The radiationdetectors (1712, 1714) may be disposed above, below, and/or between thedensity regions (1704, 1706, 1708, 1710). In some variations, eachdensity region (1704, 1706, 1708, 1710) may comprise a predetermineddepth (e.g., about 5 cm) and provide different attenuation for a beam(1732) emitted from the radiation source (1730), thereby generating dosedata corresponding to different depths.

The phantoms described herein may have a variety of shapes, as may bedesired, and may be cylinder-shaped, disk-shaped, oblong-shaped, etc. Insome variations, the phantom may be disposed on a patient supportsurface of the patient platform. In some variations, the ionizationchamber (1712) may comprise a parallel-plate chamber, cylindricalchamber, well-type chamber, free-air chamber, vented chamber, sealedchamber, combinations thereof, and/or the like. The slots (1714) maycomprise one or more shapes including rectangular, square, trapezoidal,oval or elliptical, arc-shaped (e.g., hemi-arc, hemi-spherical,hemi-cylindrical), combinations thereof, and the like. The slots (1714)may define an opening having a height sufficient to hold a radiographicsheet at a predetermined depth of the phantom (1702). In somevariations, one or more radiographic sheets (e.g., radiographic film)may be disposed between one or more of the dosimeter slots (1714).

In some variations, a patient platform may comprise a phantom that maybe used to measure the ability of a radiation detector of a radiotherapysystem (e.g., MV detector) to resolve high-contrast edges as well ascontrast resolution. For example, a phantom may comprise a set ofpatterns having variable separation and/or contrast gradients that mayallow an operator and/or the radiotherapy system to determine the upperlimit of spatial frequency and contrast resolution of the detector. Inone variation, a phantom may comprise a first region havinghigh-contrast stripes with varied spatial frequencies and a secondregion with shapes having varied intensity or contrast levels relativeto a background intensity. That is, the first region may comprise apattern with a constant intensity or contrast level, but with variablespatial frequencies to measure the ability of the detector to resolveedges (e.g., a series of stripes where the distance between them variesand/or the stripe thickness varies). The second region may comprise apattern with a constant spatial frequency (e.g., ovals of the samesize), but with variable intensity or contrast levels relative to abackground intensity to measure the ability of the detector to resolvedifferences in intensity or contrast. In this manner, a spatialfrequency and contrast resolution of one or more detectors (e.g., MVand/or kV) may be determined. The measured resolution may be compared tothe expected (e.g., calibrated) detector resolutions. As discussed inmore detail herein, a fault signal may be generated when the measuredresolution differs from a reference resolution by a predeterminedcriteria. In some variations, the phantom may be mounted to an undersideof the patient platform in a similar manner as described herein withrespect to FIGS. 16A-16B and 17 .

The phantom (1800) may include patterns that are within and beyond(e.g., above and below) the upper resolution capabilities of theradiation detector to be verified and/or calibrated. FIG. 18 depicts aplan view of a variation of a phantom (1800) having a housing (1802)comprising a first repeated pattern (1810) having a spatial frequencyrange and a second repeated pattern (1820) having a contrast range. Inparticular, the spatial frequency range may be configured to be withinand greater than an upper spatial frequency limit of a radiationdetector and the contrast range may be configured to be within andgreater than an upper contrast limit of the radiation detector. Thefirst repeated pattern (1810) and the second repeated pattern (1820) maybe spaced along a longitudinal axis (i.e., X-axis) of the phantom(1800). The housing (1802) may comprise a material such as acrylic(e.g., polymethylmethacrylate (PMMA)) or other plastic that may bedosimetrically similar to water.

The first repeated pattern (1810) and the second repeated pattern (1820)may each comprise a set of contrasting shapes spaced apart at differentintervals. When imaged by a radiation detector, the set of bars andellipsoids may generate detector data (e.g., image data). In somevariations, the first repeated pattern (1810) may comprise a set ofrectangular bars having variable separation along a longitudinal axis ofthe phantom (1800). In some variations, the second repeated pattern(1820) may comprise a first shape having a first thickness (e.g., darkellipsoid) and a second shape having a second thickness (e.g., lighterellipsoid) different from the first thickness. Additionally oralternatively, the first shape (e.g., dark ellipsoid) may have a firstdensity and a second shape (e.g., light ellipsoid) may have a seconddensity different from the first density. The first and second shapesmay comprise a material such as lead, copper, steel, acrylic, tungsten,uranium, combinations thereof, and the like.

In some variations, the repeated patterns may comprise one or moreshapes including rectangular, square, trapezoidal, oval or elliptical,arc-shaped (e.g., hemi-arc, hemi-spherical, hemi-cylindrical),combinations thereof, and the like. The housing (1802) may have avariety of shapes, as may be desired, and may be cylinder-shaped,disk-shaped, oblong-shaped, etc. In some variations, the phantom (1800)may be disposed on a patient support surface of the patient platform.

In some variations, the phantom (1800) may comprise 1, 2, 3, 4, 5, ormore repeated patterns. For example, the phantom (1800) may comprisefour repeated patterns to allow spatial frequency resolution andcontrast resolution to be determined for MV CT and kV CT detectors. Insome variations, the phantom (1800) may comprise a width (i.e., alongthe Y-axis) of between about 2 cm and about 5 cm. For example, thephantom (1800) may comprise a width of between about 3 cm and about 4cm. In some variations, the phantom (1800) may comprise a length (i.e.,along the X-axis) of between about 10 cm and about 25 cm. For example,the phantom (1800) may comprise a length of between about 15 cm andabout 20 cm. In some variations, the phantom (1800) may comprise aheight (i.e., along the Z-axis) of at least about 0.2 cm. For example,the housing (1802) of the phantom (1800) may comprise a height ofbetween about 0.5 cm and about 2 cm.

In some variations, a width of the phantom (i.e., along the Y-axis) maybe aligned parallel to a length of the patient platform. In this manner,a single beam emitted from a radiation source (not shown) may be used toimage both the first and second repeated patterns (1810, 1820) of thephantom (1800).

In some variations, the phantoms as described herein (e.g., phantoms(1602, 1702, 1800)) may be used for energy measurement, calibration,and/or verification procedures using one or more radiation detectors andtypes. Any of the phantoms and associated systems described herein maybe used in the methods described herein. The phantoms as describedherein may be disposed on top of or below a patient platform. In somevariations, the phantom may slide out laterally using a mount disposedunderneath the patient platform. The mount may allow an operator toprepare the phantom for a calibration procedure and may be configured toslidably position the phantom relative to the patient platform. Forexample, the mount may comprise a set of hand-retractable and/ormotor-driven rails. In some variations, the mount may comprise anelectrical and/or mechanical interlock configured to prevent operationof the patient platform and/or radiation source when the phantom isretracted relative to the patient platform. For example, a set ofionization chambers may be connected to an electrometer, a set ofradiographic sheets may be inserted into corresponding dosimeter slots,and the phantom may be filled with water. In some variations, one ormore ionization chambers may be loaded from a side of the phantom.Radiographic sheets disposed in respective slots may form a stack thatallows depth dose measurements to be acquired. In other variations, thephantom may be fixed relative to the patient platform.

After configuring (e.g., loading) the phantom, the patient platform maybe moved to a predetermined position relative to a radiation source anddetector. The radiation source and detector may be positioned at apredetermined gantry angle relative to the patient platform and phantom.For example, FIG. 16A illustrates the radiation source (1630) andradiation detector (1640), and the patient platform located at aposition such that a beam (1632) emitted by the radiation source (1630)irradiates a first step (1604) of the phantom (1602). Dose data acquiredby the detector (1640) based on the beam (1632) may be stored in amemory of a controller along with data including patient platformposition, gantry position, step depth, and corresponding reference data.After acquiring dose data at a first phantom position using one or moreradiation detectors, the patient platform (1620) may be movedlongitudinally to generate dose data at other phantom depths and/orusing other radiation detectors.

In some variations, dose data (e.g., dose-to-water values) may beacquired by radiographic sheets disposed in the slots of the phantom andcompared to a set of reference dose data for calibration. For example,calibrated dose intensity values may correspond to a dose received by apatient and used in offline or online dose reconstruction. In variationsof the phantom comprising a set of variable density regions, detectordata may be used to generate an beam width intensity profile. A peakvalue of the intensity profile may be set as the dose value of acorresponding ion chamber. TPR values may be calculated and compared toreference TPR values. Reference TPR values may be determined duringmachine acceptance testing and/or beam commissioning. The tissue phantomratio does not depend on absolute calibration of a radiation detectorsince variations in a calibration factor and/or radiation detector gaincancel out. Additionally or alternatively, the dose data may be used tocharacterize the stability of a radiotherapy beam. For example, beamstability may be determined during a daily quality assurance procedure.

A fault signal may be generated when the measured dose data deviatesfrom the reference dose data based on a predetermined criteria. Forexample, a fault signal may be generated by a processor when a set ofdose data measured by the detector, ionization chambers, and/orradiographic sheets exceeds a threshold parameter. A radiotherapy systemmay respond in one or more ways in response to the generation of a faultsignal. For example, the system may deactivate one or more of theradiation source and radiation detector, output the fault signal to anoperator, inhibit a radiation therapy treatment procedure, and calibratethe system using the calibration data. In some variations, the systemmay verify the fault signal and then recalibrate the system asnecessary. One or more radiation detectors may be calibrated by aprocessor using the dose data.

In variations of a phantom comprising one or more repeated patterns,dose data generated by a radiation detector may be used to generate animage of each repeated pattern using a single beam. An operator and/orprocessor may identify within the first repeated pattern (1810) andsecond repeated pattern (1820) the smallest identifiable differencebetween the shapes to thereby determine the high and low contrastresolution of the radiation detector.

In some variations, one or more visual, audio, and tactile sensoryoutput systems coupled to the system may be used to output a faultsignal and/or detector resolution to a user such as an operator. Forexample, a display coupled to the system may display the fault signal,dose data calculations, and resolution to an operator while an audiodevice may output an audible set of fault beeps and/or a verbal message.Additionally or alternatively, the fault signal and/or detectorresolution may be stored in memory and/or transmitted over a network tobe output and/or displayed to one or more of a remote operator, systemvendor, regulatory agency, and/or stored in a database.

Handheld Controller

Generally, the patient platform systems described here may comprise ahandheld, portable controller to control movement of a patient platform.FIG. 5 is a cross-sectional side view of a patient platform system(500). The system (500) may comprise a patient platform (502) coupled toa base (510). A patient (504) may be provided onto the patient platform(502). The system (500) may comprise a gantry (520) having a firstradiation source (522) and a second radiation source (530). The firstradiation source (522) may be coupled to a multi-leaf collimator (524)and may be provided opposite a first detector (528). The first radiationsource (522) may be configured to emit a first beam (526). The secondradiation source (530) may be provided opposite a second detector (534)and may be configured to emit a second beam (532). For example, thefirst radiation source (522) may be a radiation therapy source and thesecond radiation source (530) may be an imaging source.

A handheld controller (540) may be coupled to the system (500) andcomprise a first switch (542) and a docking port (544). The first switch(542) may be configured to generate a movement signal of the patientplatform (502). In some variations, the first switch (542) may compriseat least one of a button, an analog stick, a trackball, a touch screen,a directional pad, a jog dial, a motion detector, an image sensor, and amicrophone.

In other variations, the controller (540) may further comprise aproximity sensor (548) configured to detect a proximity of thecontroller (540) to the patient platform (502) or other predeterminedlocation. In some of these variations, the patient platform (502) may beconfigured to move using the movement signal and the detected proximity.For instance, control of the patient platform system (500) by thecontroller (540) may be limited to the room where the system (500) islocated and/or specific areas within the room.

The docking port (544) may be dockable with one or more of the gantry(520), and patient platform (502), and user console. The controller(540) may be configured to generate different sets of output signalsusing a docking state of the controller (540). For instance, thecontroller (540) may output a gantry movement signal only when undockedfrom the system (500), and radiotherapy treatment may be executed onlywhen the docking port (544) of the controller (540) is docked to thesystem (500).

In some other variations, the controller (540) may comprise a wirelesstransmitter outputting the movement signal (550). In other variations,the controller (540) may be wired to the system (500) to transmit themovement signal (550). In some of these variations, the movement signal(550) may control at least four degrees of freedom of motion, and mayinclude yaw and/or pitch rotation.

Additionally or alternatively, the controller (540) may comprise atether (552) for physically coupling the controller (540) to the system(500). It should be appreciated that the controller (540) may comprise aplurality of switches. Furthermore, some portions of the controller(540) may be handheld and/or portable while other portions may bestationary. For example, the controller (540) may comprise a secondswitch (546) such as a step switch or foot pedal in a housing separatefrom the first switch (542). The second switch (546) may in somevariations be a safety switch that must be engaged before a movementsignal of the first switch (542) may be outputted by the controller(540). In other variations, the controller (540) may comprise a housinghaving the first switch (542) on a first side of the housing and thesecond switch (546) on a second side of the housing opposite the firstside. For instance, the controller (540) may be configured foractivation with one hand by a thumb on the first switch (542) and afinger on the second switch (546). It should be appreciated that theshape of the controller (540) is not particularly limited. For example,the controller (540) may be pendant-shaped.

Head Fixation Device

Generally, the head fixation devices described here may fix ortemporarily hold a patient's head in a desired position duringradiotherapy treatment. FIGS. 6A-6B are side views of a patient platformsystem (600) comprising a head fixation device (610) and a patientplatform (602). The head fixation device (610) may comprise a hinge(614) coupled to a base (612), a head rest (616) coupled to the hinge(614), and a drive system (618) coupled to the head rest (616). The headrest (616) may be configured to hold a patient's head in a plurality ofangled positions. In some variations, the head rest (616) may rotateabout the hinge (614) such that the head rest (616) may pitch and yawrelative to the base (612).

In some variations, the hinge (614) may comprise a lock having aplurality of detents and pins forming a plurality of lockable positions.Accordingly, the head rest (616) may be locked relative to the base(612). In some variations, a patient may manually adjust the position oftheir head by neck flexion.

In other variations, a patient and/or operator may control a drivesystem to reposition and lock the head rest (616) in a desired position.The head rest (616) and the drive system (618) may each comprise aradiotransparent material. In some variations, the drive system (618)may comprise a pneumatic element. In other variations, the drive system(618) may comprise an electromechanical or hydraulic element. In stillother variations, the drive system (618) may be coupled to an actuator(620) and controller (not shown). For instance, the actuator (620) maybe coupled to a first end (603) of the patient platform (602). As shownin FIGS. 6A-6B, extension of the drive system (618) in a directionsubstantially perpendicular to the base (612) may angle the head to adesired position. The patient and/or operator may control the drivesystem (618) using the handheld controller to control the rate ofmovement and position of the head rest (616) until a desired position isreached. Additionally or alternatively, a patient torso and/or a patientshoulder may be coupled to the base (612). The base (612) may beremovably attached or fixed to the patient platform (602).

Controller

In some variations, the systems described herein may comprise acontroller configured to perform one or more steps of a radiotherapyprocedure. The controller may be coupled to one or more of the patientplatform and gantry. In some variations, the controller may be disposedin one or more of a patient platform, user console, and the like. Forexample, a controller may be configured to determine sag of a patientplatform, control movement and positioning of the patient platform, andperform one or more steps of a radiotherapy procedure. The controllermay comprise one or more processors and one or more machine-readablememories in communication with the one or more processors. The processormay incorporate data received from memory and patient input to controlthe system. The memory may further store instructions to cause theprocessor to execute modules, processes and/or functions associated withthe system. The controller may be configured to control one or morecomponents of the system, such as a drive system, conformable substrate,imaging system, treatment system, and the like.

The controller may be implemented consistent with numerous generalpurpose or special purpose computing systems or configurations. Variousexemplary computing systems, environments, and/or configurations thatmay be suitable for use with the systems and devices disclosed hereinmay include, but are not limited to software or other components withinor embodied on a user console, servers or server computing devices suchas routing/connectivity components, multiprocessor systems,microprocessor-based systems, distributed computing networks, personalcomputing devices, network appliances, portable (e.g., hand-held), andthe like.

The processor may be any suitable processing device configured to runand/or execute a set of instructions or code and may include one or moredata processors, image processors, graphics processing units, physicsprocessing units, digital signal processors, and/or central processingunits. The processor may be, for example, a general purpose processor,Field Programmable Gate Array (FPGA), an Application Specific IntegratedCircuit (ASIC), or the like. The processor may be configured to runand/or execute application processes and/or other modules, processesand/or functions associated with the system and/or a network associatedtherewith. The underlying device technologies may be provided in avariety of component types including metal-oxide semiconductorfield-effect transistor (MOSFET) technologies like complementarymetal-oxide semiconductor (CMOS), bipolar technologies likeemitter-coupled logic (ECL), polymer technologies (e.g.,silicon-conjugated polymer and metal-conjugated polymer-metalstructures), mixed analog and digital, combinations thereof, or thelike.

In some variations, the memory may include a database (not shown) andmay be, for example, a random access memory (RAM), a memory buffer, ahard drive, an erasable programmable read-only memory (EPROM), anelectrically erasable read-only memory (EEPROM), a read-only memory(ROM), Flash memory, combinations thereof, or the like. As used herein,database refers to a data storage resource. The memory may storeinstructions to cause the processor to execute modules, processes,and/or functions associated with the system, such as sag determinationand/or compensation, patient platform movement, and the like. In somevariations, storage may be network-based and accessible for one or moreauthorized users. Network-based storage may be referred to as remotedata storage or cloud data storage. Sensor signal and attachment datastored in cloud data storage (e.g., database) may be accessible torespective users via a network, such as the Internet. In somevariations, the database may be a cloud-based FPGA.

Some variations described herein relate to a computer storage productwith a non-transitory computer-readable medium (also may be referred toas a non-transitory processor-readable medium) having instructions orcomputer code thereon for performing various computer-implementedoperations. The computer-readable medium (or processor-readable medium)is non-transitory in the sense that it does not include transitorypropagating signals per se (e.g., a propagating electromagnetic wavecarrying information on a transmission medium such as space or a cable).The media and computer code (also may be referred to as code oralgorithm) may be those designed and constructed for a specific purposeor purposes.

Examples of non-transitory computer-readable media include, but are notlimited to, magnetic storage media such as hard disks, floppy disks, andmagnetic tape; optical storage media such as Compact Disc/Digital VideoDiscs (CD/DVDs); Compact Disc-Read Only Memories (CD-ROMs); holographicdevices; magneto-optical storage media such as optical disks; solidstate storage devices such as a solid state drive (SSD) and a solidstate hybrid drive (SSHD); carrier wave signal processing modules; andhardware devices that are specially configured to store and executeprogram code, such as Application-Specific Integrated Circuits (ASICs),Programmable Logic Devices (PLDs), Read-Only Memory (ROM), andRandom-Access Memory (RAM) devices. Other variations described hereinrelate to a computer program product, which may include, for example,the instructions and/or computer code disclosed herein.

The systems, devices, and methods described herein may be performed bysoftware (executed on hardware), hardware, or a combination thereof.Hardware modules may include, for example, a general-purpose processor(or microprocessor or microcontroller), a field programmable gate array(FPGA), an application specific integrated circuit (ASIC), or the like.Software modules (executed on hardware) may be expressed in a variety ofsoftware languages (e.g., computer code), including C, C++, Java®,Python, Ruby, Visual Basic®, and/or other object-oriented, procedural,or other programming language and development tools. Examples ofcomputer code include, but are not limited to, micro-code ormicro-instructions, machine instructions, such as produced by acompiler, code used to produce a web service, and files containinghigher-level instructions that are executed by a computer using aninterpreter. Additional examples of computer code include, but are notlimited to, control signals, encrypted code, and compressed code.

Examples of wireless communication in a wireless network include, butare not limited to cellular, radio, satellite, and microwavecommunication. The wireless communication may use any of a plurality ofcommunications standards, protocols and technologies, including but notlimited to Global System for Mobile Communications (GSM), Enhanced DataGSM Environment (EDGE), high-speed downlink packet access (HSDPA),wideband code division multiple access (W-CDMA), code division multipleaccess (CDMA), time division multiple access (TDMA), Bluetooth,near-field communication (NFC), radio-frequency identification (RFID),Wireless Fidelity (Wi-Fi) (e.g., IEEE 802.11a, IEEE 802.11b, IEEE802.11g, IEEE 802.11n), Voice over Internet Protocol (VoIP), Wi-MAX, aprotocol for email (e.g., Internet Message Access Protocol (IMAP), PostOffice Protocol (POP)), instant messaging (e.g., eXtensible Messagingand Presence Protocol (XMPP), Session Initiation Protocol for InstantMessaging, Presence Leveraging Extensions (SIMPLE), Instant Messagingand Presence Service (IMPS)), Short Message Service (SMS), or any othersuitable communication protocol. Some wireless network deploymentscombine networks from multiple cellular networks or use a mix ofcellular, Wi-Fi, and satellite communication.

In some variations, a wireless network may connect to a wired network inorder to interface with the Internet, other carrier voice and datanetworks, business networks, and personal networks. A wired network istypically carried over copper twisted pair, coaxial cable, and/or fiberoptic cables. There are many different types of wired networks includingwide area networks (WAN), metropolitan area networks (MAN), local areanetworks (LAN), Internet area networks (IAN), campus area networks(CAN), global area networks (GAN), like the Internet, and virtualprivate networks (VPN). As used herein, network refers to anycombination of wireless, wired, public, and private data networks thatare typically interconnected through the Internet, to provide a unifiednetworking and information access system.

II. Methods

Methods of Performing Radiotherapy

Generally described here are methods for performing radiotherapy. Any ofthe systems and devices described herein may be used in the radiotherapyprocedures described below. FIG. 7 is a flowchart that generallydescribes a radiotherapy process (700) including sag determination andcompensation. The process (700) may include loading a patient onto apatient platform (702). In some variations, patient loading may comprisesecuring one or more portions of the patient relatively comfortably sothat they remain substantially in place relative to the patientplatform. As discussed further in FIG. 10 , a conformable substrate ofthe patient platform may be controlled to couple a patient to thepatient platform to increase patient compliance with radiotherapytreatment. In some variations, the height of the conformable substratemay be independently controlled to contour the patient platform to thepatient's shape (e.g., FIGS. 2A-2C). Patient platform settings for eachpatient may be stored in memory and reapplied for efficiency andrepeatability across one or more patient platforms and/or radiotherapysystems and across treatment sessions.

Additionally or alternatively, a patient platform may be contoured to apatient's body shape through heating and cooling of a thermoelectriclayer. In yet other variations, as discussed with respect to FIGS. 6A-6Band further in FIG. 14 , a patient head may be coupled by a headfixation device to a patient platform in a fixed position. Duringadjustment of the head fixation device, the patient may control thepivoting of the head through neck flexion to improve patient comfort andcompliance.

Once a patient is loaded onto the patient platform, the patient platformmay be moved into a patient region of a gantry (704). In somevariations, as discussed with respect to FIGS. 3A-3D and further inFIGS. 11A-11B, the patient platform may comprise a plurality of portionsthat may move or telescope in an axial direction relative to each other.An upper portion of the patient platform may be formed of aradiotransparent material while a lower portion may be formed of astiffer material that is radiopaque and that exhibits less sag than theradiotransparent material. The patient platform may be moved into thepatient region such that the radiopaque portion does not cross the planeof an imaging beam and/or treatment beam when either or both of thesebeams are activated. Accordingly, the length of the radiotransparentupper portion cantilevered from a base may be reduced to reduce anamount of sag of the patient platform. In some variations, the upperportion may have a length of 0.25-2.0 meters.

In other variations, as discussed further in FIGS. 12 and 13A-13E, thepatient platform may be moved to align one or more regions of interestof a patient (e.g., lesion, tumor) to an isocenter of a gantry to ensurethat a radiation dose is delivered to the region of interest. Inparticular, as used herein in reference to imaging and radiationoncology, the isocenter is the point in space through which a pluralityof beamlets intersect, the plurality of beamlets being emitted from aplurality of gantry locations by a rotating radiation source. Thepatient platform may translate (axially and/or laterally) and rotate(pitch and/or yaw) to position a region of interest on an isocenter toprovide a desired radiation dose.

In yet other variations, as discussed in further detail below, patientplatform sag may be determined (706), compensated for (708) and used todetermine or revise treatment beam parameters (710) such as power,duration, location, etc. (e.g., treatment plan). In some variations, asdiscussed with respect to FIGS. 1A-1F, an imaging beam may be emittedtowards a sagging patient platform and used to determine a differencebetween an unweighted position and weighted position of the patientplatform. For example, the patient platform may be imaged prior toloading a patient to determine a position of the unweighted patientplatform. A change in location of the patient platform may be determinedand then used to determine a change in location of the patient and oneor more regions of interest. In some instances, the change in locationof the patient platform may be used to compensate for the patientplatform sag (708). For example, the treatment plan may be modified,adjusted, and/or updated to compensate for the determined sag.Alternatively or additionally, a height and/or position of the patientplatform may be adjusted (e.g., raised or lowered) to compensate for thesag of the patient platform in the treatment beam plane.

Once the patient platform is in a desired position and the treatmentplan parameters have been updated or adjusted to compensate for sag (ifneeded), a treatment beam may be emitted (712) according to thetreatment plan. After execution of the treatment plan, the patientplatform may be removed from the patient region of the gantry (714).

Determine Sag of a Patient Platform

FIG. 8 is a flowchart of one variation of a patient platform sagdetermination process (800). This method may be used with, for example,the systems depicted in FIGS. 1A-1F, where the patient platform iscoupled to an elongate element and/or optical marker. The process mayinclude emitting a first beam by a radiation source through a collimatorto irradiate an elongate element coupled to the patient platform (802).The first beam may be directed toward the elongate element withoutintersecting the patient in order to limit exposure to the patient. Thefirst beam may be received by a detector (804) that is located oppositethe radiation source and collimator. Alternatively, an optical sensormay receive light reflected from an optical marker. A controller usingthe received detector data may then determine a first location of theelongate element within the imaging beam plane (806) corresponding tothe unweighted patient platform. In some variations, the patientplatform sag determination may be performed prior to the patientreceiving radiotherapy treatment. However, patient platform sagdetermination may be determined during radiotherapy treatment asnecessary for recalibration.

FIG. 9 is a flowchart of one variation of a process (900) that describesin more detail the step of determining a location of the elongateelement and/or optical marker (806) using a Winston-Lutz based method.The elongate element and/or optical marker may be detected at aplurality of angles to generate detector data that indicates thelocation of the elongate element and/or optical marker (902). Forinstance, the elongate element may be imaged at a set of cardinal angles(e.g., 0°, 180°, 270°) and/or other angles. The image data may beanalyzed by a processor to locate the elongate element and/or opticalmarker (904). The image data may then be compared to reference datacorresponding to the elongate element and/or optical marker of anunweighted platform (906).

Such reference data may be acquired, for example, before the patient isloaded onto the platform, and/or may be reference data acquired andstored during calibration and/or setup procedures. The differencesbetween the data may then be used to determine the location of theelongate element and/or optical marker (908) and the degree to which ithas changed from the reference location of the elongate element and/oroptical marker (i.e., sag).Turning back to FIG. 8 , a relationshipbetween the location of the elongate element and/or optical marker andthe patient platform may be known or previously determined. Accordingly,a change in a patient platform location (808) between an unweighted andweighted state may be determined. Accordingly, a change in the locationof one or more regions of interest of a patient may be determined basedon the sag of the patient platform. Additionally or alternatively, theposition of the patient platform and/or treatment plan may be modifiedto compensate for the sag of the patient platform (810).

Load Patient onto Patient Platform

FIG. 10 is a flowchart of one variation of a patient platform loadingprocess (1000). This method may be used with the system depicted in FIG.2C. The method (1000) may include heating a thermoelectric layer of apatient platform (1002). The thermoelectric layer may be heated to forma compliant configuration for a patient to lay on. The thermoelectriclayer of the patient platform may then be modified through patient bodyweight to form an ergonomic surface. In other variations, the patientplatform may comprise a conformable substrate having a plurality ofenclosures. In some variations, the loading process (1000) may beginwith the heights of the plurality of enclosures being set to apredetermined height (1004) based on a previous fitting for the patientor based on predetermined data for the patient's height and weight. Apatient may then be loaded onto a patient platform (1006). In someinstances, the patient lays down on the patient platform in apredetermined direction outside a patient region of a gantry. It shouldbe appreciated that the determination and setting of a patientconfiguration of the patient platform may occur outside the gantry(e.g., in a patient set-up or waiting area) to reduce the time thepatient spends within the gantry, thereby allowing more efficient use ofa radiotherapy system.

Once the patient is loaded onto of the patient platform, a pressure ofthe plurality of enclosures may be measured (1008) using a pressuresensor coupled to the patient platform. The pressure may comprise aplurality of enclosure pressures. The height of each of the plurality ofenclosures may be independently controlled using the plurality ofenclosure pressures such that the patient platform contours to a shapeof the patient (1010). Additionally or alternatively, the thermoelectriclayer may be cooled to transition from the compliant configuration to arigid configuration (1012). In some instances, the heating of thethermoelectric layer may be stopped. In other instances, thethermoelectric layer may be actively cooled to form the rigidconfiguration. It should be appreciated that the heating and coolingsteps (1002, 1012) may not be performed where the patient platform doesnot have a thermoelectric layer.

In some variations, a patient configuration may be determined (1014)corresponding to the height of each of the plurality of enclosures. Thepatient configuration may comprise at least one of the pressure and/orheight of the plurality of enclosures. The patient configuration may bestored in memory (1016) and/or transferred to one or more other patientplatforms and/or radiotherapy systems. Subsequently, the height of theplurality of enclosures may be readjusted using the stored patientconfiguration (1018). Thus, patient registration time may be reduced toincrease efficiency and improve imaging and/or treatment consistency.

Move Patient Platform

FIGS. 11A-11B are flowcharts of variations of processes (1100, 1150) formoving a patient platform into a gantry to reduce and/or determine sag.In some variations, the methods may be performed by a patient platformcoupled to a base. In FIG. 11A, the patient platform may comprise anupper portion and a lower portion coupled to the upper portion where theupper portion and lower portion may move relative to each other. Thelower portion may have higher rigidity than an upper portion. In somevariations, the upper portion may comprise a radiotransparent firstmaterial and the lower portion may comprise a radiopaque secondmaterial. The lower portion may comprise any material that issufficiently rigid to support the upper portion, regardless of itsradiopacity and/or radiotransparency.

The process (1100) of FIG. 11A may include moving the lower portion ofthe patient platform relative to a patient region of a gantry (1102).The upper portion may move relative to the lower portion (1104). Animaging beam may be emitted (1106). In some variations, the imaging beammay be emitted by an imaging radiation source in an imaging planeperpendicular to a longitudinal axis of the patient platform. Movementof the lower portion and upper portion may be such that the lowerportion is non-intersecting with the imaging plane and the upper portionintersects the imaging plane. In some of these variations, moving theupper portion into the imaging plane comprises positioning the lowerportion such that a leading edge of the lower portion is located at apredetermined first distance away from the imaging plane. The platformmay move longitudinally through (e.g., stepped through) the imaging beamacross a distance that corresponds to the length of the radiotransparentupper portion that is cantilevered from the lower portion. The imagingbeam may capture images of the portion of the patient that is locatedalong the length of the upper portion that is cantilevered from thelower portion.

In other variations, the process (1100) may include moving the lowerportion relative to the base (1108) and moving the upper portionrelative to the lower portion (1110). A treatment beam may be emitted(1112) from a treatment radiation source coupled to a multi-leafcollimator in a treatment plane perpendicular to a longitudinal axis ofthe patient platform. The upper portion and the lower portion may bemoved such that the lower portion is non-intersecting with the treatmentplane and the upper portion intersects the treatment plane. In some ofthese variations, moving the upper portion into the treatment planecomprises positioning the lower portion such that the leading edge ofthe lower portion is located at a predetermined second distance awayfrom the treatment plane.

FIG. 11B illustrates another variation of a process (1150) that may beperformed by a patient platform coupled to a base. The patient platformmay comprise an upper portion and a lower portion fixed to the upperportion. The lower portion of the patient platform may be coupled to thebase such that the lower portion may move relative to the base. In somevariations, the lower portion may have higher rigidity than the upperportion. The upper portion and the lower portion may comprise materialshaving different degrees of radiotransparency. For instance, the upperportion may comprise a radiotransparent first material and the lowerportion may comprise a radiopaque second material.

The process (1150) of FIG. 11B may include moving the patient platformrelative to a base (1152). An imaging beam may be emitted by an imagingradiation source in an imaging plane perpendicular to a longitudinalaxis of the patient platform (1154). In some variations, the patientplatform is moved such that only an upper portion of the patientplatform intersects with the imaging beam (1156). For instance, movementof the lower portion and upper portion may be such that the lowerportion is non-intersecting with the imaging plane and the upper portionintersects the imaging plane. In some of these variations, the lowerportion may be moved such that a leading edge of the lower portion islocated at a predetermined first distance away from the imaging plane.The upper portion may move relative to the lower portion and intersectthe imaging plane.

In one variation, the process (1150) may include moving the patientplatform relative to the base (1158). A treatment beam may be emitted(1160) by a treatment radiation source coupled to a multi-leafcollimator in a treatment plane perpendicular to a longitudinal axis ofthe patient platform. In some variations, the patient platform may bemoved such that only an upper portion of the patient platform intersectswith the treatment beam (1162). For instance, the patient platform maybe moved such that the lower portion is non-intersecting with thetreatment plane and the upper portion intersects the treatment plane. Insome of these variations, the lower portion may be moved such that theleading edge of the lower portion is located at a predetermined seconddistance away from the treatment plane. The upper portion may moverelative to the lower portion and intersect the treatment plane.

Move Region of Interest to Isocenter

For a radiotherapy procedure, it may be desirable to position the centerof a region of interest at the isocenter of a gantry. In the processesdescribed below, one or more regions of interest may be moved to alignto an isocenter such as through movement of a patient platform. FIG. 12is a flowchart of one variation of a patient platform moving process(1200). In some variations, the process (1200) may include determining alocation of a first region of interest (1202) of a patient on a patientplatform. In some of these variations, a location of a second region ofinterest may be determined (1204). The patient platform may then bemoved into a patient region of a gantry (1206), as illustrated inexemplary FIG. 13A. The gantry may define an isocenter point about whichthe gantry rotates and an isocenter axis comprising the isocenter pointand extending in parallel with a longitudinal axis of the patientregion. FIG. 13A illustrates a patient platform system (1300) comprisinga patient platform (1310) moved into a patient region of a gantry(1330). The gantry (1330) may comprise a radiation source (1332) coupledto a multi-leaf collimator (1334). A treatment beam (1336) may beemitted by the radiation source (1332). A patient (1320) may be loadedon the patient platform (1310) and may comprise a first region ofinterest (1322) having a first longitudinal axis (1323) and a secondregion of interest (1324) having a second longitudinal axis (1325). Asshown in FIG. 13A, an isocenter axis (1338) is substantially parallel toboth first and second regions of interest (1322, 1324).

Turning back to FIG. 12 , the patient platform may move laterally alongthe Y-axis to position the first region of interest on the isocenteraxis (1208). In some variations, the patient platform may be moved inone or more of pitch and yaw rotation and a lateral direction. Tofurther improve radiotherapy treatment, the patient platform may bemoved to align a longitudinal axis of the first region of interest onthe isocenter axis (1210). As shown in FIG. 13B, the patient platform(1310) may be moved laterally along the Y-axis to align the firstlongitudinal axis (1323) onto the isocenter axis (1338). A radiationbeam may be emitted from a radiation source to the first region ofinterest on the isocenter axis (1212).

After treatment of the first region of interest, the patient platformmay be moved to position the second region of interest on the isocenteraxis (1214). In some variations, the patient platform may be moved toalign a longitudinal axis of the second region of interest on theisocenter axis (1216). As shown in FIG. 13C, the patient platform (1310)may be moved laterally along the Y-axis to align the second longitudinalaxis (1325) onto the isocenter axis (1338). A radiation beam may beemitted from the radiation source to the second region of interest onthe isocenter axis (1218). Of course, the patient platform (1310) may bemoved to treat any number of regions of interest of a patient (1320).

If a region of interest changes position at any point before, during, orafter radiotherapy treatment due to patient movement on the patientplatform (due to breathing, patient discomfort, and the like), thepatient platform may be moved to compensate for the patient's change inposition using a patient platform controller. For example, if a patientrolls in one direction on the patient platform, the position of thepatient platform may be adjusted or rolled in the opposite direction tocompensate for the patient's movement. In some variations, the methodsdescribed with respect to FIGS. 12 and 13A-13D may be performed usingthe system described with respect to FIGS. 4A-4E.

FIG. 13D illustrates another variation where a longitudinal axis (1323)of a region of interest (1322) of patient (1320) is non-parallel to anisocenter axis (1338). The patient platform (1310) may be yawed aboutthe Z-axis to align the longitudinal axis (1323) to the isocenter axis(1338), as shown in FIG. 13E. In some non-limiting, exemplaryvariations, the patient platform (1310) may yaw about the Z-axis by upto about 15°. Although not illustrated, it should be appreciated thatthe pitch of the patient platform may be changed to align a longitudinalaxis of a region of interest to an isocenter axis.

Position a Patient Head

FIG. 14 is a flowchart of one variation of a patient head positioningprocess (1400). In some variations, the process (1400) may includeloading a patient onto a patient platform (1402). A head fixation devicemay be provided on the patient platform such that a patient head may becoupled to a head rest of the head fixation device (1404). In somevariations, a patient head may be held or fixed to the head rest. Thehead may then be pivoted about a hinge of the head fixation device(1406). The head rest may pitch and yaw relative to the patientplatform. The pivoting may be provided by a head rest drive systemcoupled to the head rest and/or by patient neck flexion. For instance, aradiotransparent pneumatic element may be extended substantiallyvertically tilt the head rest and to position the patient head at adesired angle. Once the head is at a desired position, the head rest maybe locked (1408). One or more portions of a patient body may optionallybe coupled to the platform (1410). For instance, a patient torso and/orshoulder may be coupled to the head fixation device and/or patientplatform.

Although the foregoing variations have, for the purposes of clarity andunderstanding, been described in some detail by of illustration andexample, it will be apparent that certain changes and modifications maybe practiced, and are intended to fall within the scope of the appendedclaims. Additionally, it should be understood that the components andcharacteristics of the systems and devices described herein may be usedin any combination. The description of certain elements orcharacteristics with respect to a specific figure are not intended to belimiting or nor should they be interpreted to suggest that the elementcannot be used in combination with any of the other described elements.For all of the variations described above, the steps of the methods maynot be performed sequentially. Some steps are optional such that everystep of the methods may not be performed.

We claim:
 1. A system comprising: a patient platform having alongitudinal axis, a patient support surface, and an underside surfaceopposite the patient support surface; and a phantom mounted to theunderside surface, the phantom comprising a plurality of radiationdetectors arranged along the longitudinal axis of the patient platform,wherein the phantom further comprises a plurality of steps, each stephaving a corresponding predetermined depth, wherein each of theradiation detectors are disposed at the predetermined depth of itscorresponding step.
 2. The system of claim 1, wherein the radiationdetectors each comprise a dosimeter slot and an ionization chamber ateach corresponding step.
 3. The system of claim 2, wherein the dosimeterslots are parallel to the longitudinal axis and wherein each of theslots is disposed at the predetermined depth of its corresponding step.4. The system of claim 2, wherein the ionization chamber for each stepis aligned along the longitudinal axis.
 5. The system of claim 2,wherein the ionization chamber for each step is offset along thelongitudinal axis.
 6. The system of claim 2, further comprising aradiographic sheet for each step, configured to fit within the dosimeterslot for each corresponding step.
 7. The system of claim 1, whereinionization chambers are arranged along a longitudinal axis of thephantom and along a vertical axis perpendicular to the longitudinal axisof the phantom.
 8. The system of claim 1, further comprising dosimeterslots, wherein at least one of the dosimeter slots is nearly parallel toa vertical axis perpendicular to a longitudinal axis of the phantom. 9.The system of claim 1, wherein the phantom comprises a housing thatdefines an internal fluid-tight volume.
 10. The system of claim 1,further comprising a mount coupling the phantom to the patient platform.11. The system of claim 10, wherein the mount is configured to slidablyposition the phantom relative to the patient platform.
 12. The system ofclaim 1, wherein the radiation detectors each comprise an ionizationchamber and a corresponding dosimeter slot.
 13. The system of claim 12,wherein each dosimeter slot intersects its corresponding ionizationchamber.
 14. The system of claim 12, wherein the ionization chambers anddosimeter slots are spaced apart from each other along the longitudinalaxis.
 15. The system of claim 1, further comprising a handheldcontroller comprising a first switch and a docking port, wherein thefirst switch is configured to generate a movement signal.
 16. The systemof claim 15, wherein the first switch comprises at least one of abutton, an analog stick, a trackball, a touch screen, a directional pad,a jog dial, a motion detector, an image sensor, and a microphone. 17.The system of claim 15, wherein the handheld controller comprises awireless transmitter outputting the movement signal.
 18. The system ofclaim 15, further comprising a tether coupled to the patient platformand the handheld controller.
 19. The system of claim 15, wherein themovement signal controls at least four degrees of freedom of motion. 20.The system of claim 15, further comprising a second switch.
 21. Thesystem of claim 20, wherein the handheld controller is configured tooutput the movement signal upon activation of the first and secondswitches.
 22. The system of claim 20, wherein the handheld controllercomprises the second switch and a housing, and wherein the first switchis provided on a first side of the housing and the second switch isprovided on a second side of the housing opposite the first side. 23.The system of claim 20, wherein the second switch is a step switch. 24.The system of claim 1, further comprising a head fixation comprising ahinge coupled to a base, a head rest coupled to the hinge, and a drivesystem coupled to the head rest, wherein the drive system is configuredto extend substantially perpendicularly to the base, wherein the headrest and the drive system each comprise a radiotransparent materialsubstantially transparent to high energy photons.
 25. The system ofclaim 24, wherein the drive system comprises a pneumatic element. 26.The system of claim 24, wherein the drive system comprises anelectromechanical element.
 27. The system of claim 24, furthercomprising an actuator coupled to the drive system, wherein the actuatoris coupled to a first end of the patient platform.
 28. The system ofclaim 24, wherein the hinge comprises a lock, and wherein the lockcomprises a plurality of detents and a pin.
 29. The system of claim 1,wherein the phantom further comprises a first region having a firstdensity and a second region having a second density different from thefirst density, and wherein the regions are arranged along thelongitudinal axis.
 30. The system of claim 29, wherein the first regionand the second region have a same thickness.
 31. The system of claim 29,further comprising a third region having a third density that isdifferent from the first density and the second density.
 32. The systemof claim 1, wherein the phantom is located in a phantom region of thepatient platform that does not overlap with a patient region of thepatient platform.
 33. The system of claim 1, wherein each step comprisesa same material.
 34. The system of claim 1, wherein each step comprisesdifferent materials that have different densities and/or attenuationproperties.
 35. A system comprising: a radiation detector; a patientplatform having a longitudinal axis, a patient support surface, and anunderside surface opposite the patient support surface; and a phantommounted to the underside surface, the phantom comprising a firstrepeated pattern having a spatial frequency range and a second repeatedpattern having a contrast range, wherein the first and second repeatedpatterns are spaced along a longitudinal axis of the phantom, andwherein the spatial frequency range is within a spatial frequency limitof the radiation detector and the contrast range is within a contrastlimit of the radiation detector.
 36. The system of claim 35, wherein thefirst and second repeated patterns comprise a set of contrasting shapesspaced apart at different intervals.
 37. The system of claim 36, whereinthe set of shapes comprises a first shape having a first thickness and asecond shape having a second thickness different from the firstthickness.
 38. The system of claim 36, wherein the set of shapescomprises a first shape having a first density and a second shape havinga second density different from the first density.
 39. The system ofclaim 35, wherein the first repeated pattern comprises rectangular barshaving a constant contrast level and having varied spatial frequencies.40. The system of claim 35, wherein the phantom is disposed within animaging region of the patient platform.
 41. The system of claim 35,further comprising a mount coupling the phantom to the patient platform.42. The system of claim 35, wherein the second repeated patterncomprises a plurality of shapes having a constant spatial frequency andhaving varied contrast levels.
 43. The system of claim 42, wherein theplurality of shapes comprises ovals.